Photoresist composition and process of producing photoresist pattern

ABSTRACT

A photoresist composition comprising
     a resin having an acid-labile group and no fluorine atom,   a resin having a fluorine atom, and   a salt represented by formula (I):

This nonprovisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2014-075969 filed in JAPAN on Apr. 2, 2014,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a photoresist composition and aprocess of producing photoresist pattern.

BACKGROUND ART

At to a photoresist composition to be used for semiconductormicrofabrication, JP2006-257078A1 discloses a salt for an acidgenerator, represented by formula (B2).

JP2011-102934A1 discloses a photoresist composition which comprises asalt of formula (B3), a resin having the structural units of formula(B4), a nitrogen-containing organic compound of formula (D)-4 and anorganic solvent.

SUMMARY OF THE DISCLOSURE

The present invention relates to the followings:

[1] A photoresist composition comprising

a resin having an acid-labile group and no fluorine atom,a resin having a fluorine atom, anda salt represented by formula (I):

in which X represents a sulfur atom or an iodine atom;m represents 0 or 1;R¹ represents a C1-C12 fluoroalkyl group;R² and R³ each independently represent a C1-C12 hydrocarbon group inwhich a hydrogen atom can be replaced by a substituent and in which amethylene group can be replaced by an oxygen atom, a sulfur atom or acarbonyl group, or R² and R³ are optionally bond to each other and forma ring together with together with X⁺ when X is a sulfur atom; andZ⁻ represents an organic anion.

[2] The photoresist composition according to [1] wherein R² represents aC6-C12 aromatic hydrocarbon group in which a hydrogen atom can bereplaced by a substituent.

[3] The photoresist composition according to [1] or [2] wherein Z⁻represents an organic anion represented by formula (I-A):

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group,L^(b1) represents a C1-C24 divalent saturated hydrocarbon group in whicha methylene group can be replaced by —O— or —CO— and in which a hydrogenatom can be replaced by a fluorine atom or a hydroxy group, andY represents a methyl group which may have a substituent or a C3-C18alicyclic hydrocarbon group which can have a substituent and in which amethylene group can be replaced by —O—, —CO— or —SO₂—.

[4] The photoresist composition according to any one of [1] to [3]wherein the resin having a fluorine atom comprises a structural unitrepresented by formula (a4-0), formula (a4-2), formula (a4-3), orformula (a4-4):

wherein R⁵ represents a hydrogen atom or a methyl group;L⁴ represents a single bond or a C1-C4 aliphatic saturated hydrocarbongroup;L³ represents a C1-C8 perfluoroalkanediyl group; andR⁶ represents a hydrogen atom or a fluorine atom;

wherein R^(f1) represents a hydrogen atom or a methyl group;A^(f1) represents a C1-C6 alkanediyl group; andR^(f2) represents a C1-C10 hydrocarbon group having a fluorine atom;

wherein R^(f11) represents a hydrogen atom or a methyl group;A^(f11) represents a C1-C6 alkanediyl group;A^(f13) represents a C1-C18 aliphatic hydrocarbon group which may have afluorine atom;X^(f12) represents a carbonyloxy group or an oxycarbonyl group;A^(f14) represents a C1-C17 aliphatic hydrocarbon group which may have afluorine atom, provided that one or both of A^(f13) and A^(f14)represents a fluorine-containing aliphatic hydrocarbon group;

wherein R^(f21) represents a hydrogen atom or a methyl group;A^(f21) represents —(CH₂)_(j1)—, —(CH₂)_(j2)—O—(CH₂)_(j3)— or—(CH₂)_(j4)—CO—O—(CH₂)_(j5)— where j1, j2, j3, j4 or j5 eachindependently represent an integer of 1 to 6; andR^(f22) represents a C1-C10 hydrocarbon group having a fluorine atom.

[5] The photoresist composition according to any one of [1] to [4] whichfurther comprises a salt which generates an acid having acidity weakerthan an acid generated from the salt represented by formula (I).

[6] The photoresist composition according to [5] wherein the salt whichgenerates an acid having acidity weaker than an acid generated from thesalt represented by formula (I) is a compound represented by formula(D):

wherein R^(D1) and R^(D2) each independently represent a C1-C12monovalent hydrocarbon group, a C1-C6 alkoxy group, a C2-C7 acyl group,a C2-C7 acyloxy group, a C2-C7 alkoxycarbonyl group, a nitro group or ahalogen atom; andthe symbols m′ and n′ each independently represent an integer of 0 to 4.

[7] A process for producing a photoresist pattern comprising thefollowing steps (1) to (5):

-   -   (1) a step of applying the photoresist composition according any        one of [1] to [6] on a substrate,    -   (2) a step of forming a composition film by conducting drying,    -   (3) a step of exposing the composition film to radiation,    -   (4) a step of baking the exposed composition film, and    -   (5) a step of developing the baked composition film.

DESCRIPTION OF PREFERRED EMBODIMENTS Photoresist Composition

The photoresist composition of the disclosure comprises

a resin having an acid-labile group and no fluorine atom,a resin having a fluorine atom, anda salt represented by formula (I):

In formula (I), X represents a sulfur atom or an iodine atom;

m represents 0 or 1;R¹ represents a C1-C12 fluoroalkyl group;R² and R³ each independently represent a C1-C12 hydrocarbon group inwhich a hydrogen atom can be replaced by a substituent and in which amethylene group can be replaced by an oxygen atom, a sulfur atom or acarbonyl group, or, R² and R³ are optionally bond to each other and forma ring together with together with X⁺ when X is a sulfur atom; andZ⁻ represents an organic anion.

In formula (I), provided that X is a sulfur atom, “m” represents 1.Provided that X is an iodine atom, “m” represents 0.

Examples of the fluoroalkyl group represented by R¹ includetrifluoromethyl group, difluoromethyl group, a perfluoroethyl group, a1,1,1-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, aperfluoropropyl group, a 1,1,1,2,2-pentafluoropropyl group,perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a1,1,1,2,2-pentafluorobutyl group, a perfluoropentyl group, aperfluorohexyl group, a 1,1,1,2,2,3,3,4,4-nonafluorohexyl group, a1,1,1,2,2-pentafluorohexyl group, preferably a C1-C6 fluoroalkyl group,and more preferably one represented by formula (I-e):

in which the symbol “r” represents an integer of 0 to 4 and the symbol“t” represents an integer of 1 to 3 provided that the total of r and tis 6 or less.

The hydrocarbon groups represented by R² or R³ include an alkyl group,an alicyclic hydrocarbon group, an aromatic hydrocarbon group andcombination of the groups selected therefrom.

Examples of the alkyl group include a methyl group, an ethyl group, ann-propyl group, an isopropyl group, an n-butyl group, an isobutyl group,a tert-butyl group, a pentyl group, a hexyl group, an octyl group, anonyl group, a decyl group, an undecyl group and a dodecyl group.

The alicyclic hydrocarbon group may be monocyclic or polycyclic.

Examples of the monocyclic alicyclic hydrocarbon group include acycloalkyl group such as a cyclopentyl group, a cyclohexyl group, acycloheptyl group, a cyclooctyl group, a cyclononyl group and acyclododecyl group. Examples of the polycyclic alicyclic hydrocarbongroup include a decahydronaphtyl group, an adamantyl group, a2-alkyladamantane-2-yl group, a 1-(adamantane-1-yl)alkane-1-yl group, anorbornyl group, a methylnorbornyl group and an isonorbornyl group.

Examples of the aromatic hydrocarbon group include a phenyl group, anaphthyl group or a tolyl group.

Examples of the combination for R² and R² include an aralkyl group suchas a benzyl group and a 1-phenylethyl group, and an alkyl-substitutedaromatic hydrocarbon group.

Examples of the substituent for the hydrocarbon group represented by R²and R² include a halogen atom such as a fluorine atom, a hydroxy group,an alkoxy group such as methoxy group or ethoxy group, and a haloalkylgroup such as C1-C6 fluoroalkyl group.

R² and R³ are in each occurrence preferably an aromatic hydrocarbongroup in which a hydrogen atom can be replaced by a substituent, morepreferably a C6-C12 aromatic hydrocarbon group in which a hydrogen atomcan be replaced by a substituent, still more preferably a phenyl groupin which a hydrogen atom can be replaced by a substituent or a naphtylgroup in which a hydrogen atom can be replaced by a substituent, furthermore preferably a phenyl group in which a hydrogen atom can be replacedby a substituent.

R² and R³ are preferably the same hydrocarbon group each other, or aring formed by bonding them each other together with ⁺S. The ring isbonded to R¹ and form a sulfonium. The sulfonium may have an oxygen atomor a carbonyl group in the structure thereof. Examples of the ringinclude a C2-C5 cyclic hydrocarbon sulfonium, such as a thiolan-1-iumring (tetrahydrothiphenium ring), a thian-1-ium ring and a1,4-oxathian-4-ium ring.

X represents preferably a sulfur atom.

Specific examples of the cation in formula (I) include the followingones.

The cation in formula (I) is preferably one represented by formula(I-c-1), (I-c-2), (I-c-4), (I-c-6), (I-c-7), (I-c-10), (I-c-11),(I-c-25), (I-c-34) or (I-c-35), more preferably one represented byformula (I-c-1), (I-c-2), (I-c-4), (I-c-6), (I-c-7), (I-c-10) or(I-c-11), or (I-c-25).

Examples of the organic cation represented by Z⁻ include a sulfonic acidanion, a sulfonylimide anion, a sulfonylmethide anion and carboxylicacid anion. Z⁻ preferably represents an organic anion represented byformula (I-A):

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group,L^(b1) represents a C1-C24 divalent saturated hydrocarbon group in whicha methylene group can be replaced by —O— or —CO—, and in which ahydrogen atom can be replaced by a fluorine atom or a hydroxy group, andY represents a methyl group which may have a substituent or a C3-C18alicyclic hydrocarbon group which can have a substituent and in which amethylene group can be replaced by —O—, —CO— or —SO₂—.

Examples of the perfluoroalkyl group represented by Q¹ or Q² include atrifluoromethyl group, a pentafluoroethyl group, a heptafluoropropylgroup, a nonafluorobutyl group, an undecafluoropentyl group and atridecafluorohexyl group, and a trifluoromethyl group is preferable. Q¹and Q² each independently preferably represent a fluorine atom or atrifluoromethyl group, and Q¹ and Q² are more preferably fluorine atoms.

Examples of the divalent saturated hydrocarbon group represented byL^(b1) include a chain or branched alkandiyl group, a monocyclic orpolycyclic divalent saturated hydrocarbon group and a group formed bycombining two or more groups selected from the group consisting of thealkandiyl group and the monocyclic or polycyclic divalent saturatedhydrocarbon group.

Examples thereof include a linear alkanediyl group such as a methylenegroup, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diylgroup, a pentane-1,5-diyl, a hexane 1,6diyl group, a heptane-1,7-diylgroup, an octane-1,8-diyl group, a nonane-1,9-diyl group, adecane-1,10-diyl group, an undecane-1,11-diyl group, adodecane-1,12-diyl group, a tridecane-1,13-diyl group, atetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, ahexadecane-1,16-diyl group and a heptadecane-1,17-diyl group,

a branched chain alkanediyl group such as a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group, a monocyclicdivalent saturated hydrocarbon group such as a cyclobutane-1,3-diylgroup, a cyclopentane-1,3-diyl group, a cyclohexane-1,2-diyl group, a1-methylcyclohexane-1,2-diyl group, a cyclohexane-1,4-diyl group, acyclooctane-1,2-diyl group and a cyclooctane-1,5-diyl group, anda polycyclic divalent saturated hydrocarbon group such as anorbornane-1,4-diyl group, a norbornane-2,5-diyl group and anadamantane-2,6-diyl group.

Examples of the aliphatic hydrocarbon group in which a methylene grouphas been replaced by —O— or —CO— include those represented by formulae(b1-1), (b1-2) and (b1-3).

In formula (b1-1), L^(b2) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, and L^(b3) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by ahydroxyl group or a fluorine atom and where a methylene group may bereplaced by an oxygen atom or carbonyl group, provided that total numberof the carbon atoms of L^(b2) and L^(b3) is up to 22.

In formula (b1-2), L^(b4) represents a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, and L^(b5) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or carbonyl group, provided that the total carbon atomsof L^(b4) and L^(b5) is up to 22.

In formula (b1-3), L^(b6) represents a single bond or a C1-C23 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, and L^(b7) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by ahydroxyl group or a fluorine atom and where a methylene group may bereplaced by an oxygen atom or carbonyl group, with the proviso thattotal carbon number of L^(b6) and L^(b7) is up to 23 and with theproviso that formula (b1-3) excludes group having a structurerepresented by -L^(b6)-O—CO—.

In these formulae, * represents a binding position, * of the left siderepresents a binding position to —C(Q¹)(Q²)-, and * of the right siderepresents a binding position to Y.

In formulae (b1-1), (b1-2) and (b1-3), the divalent saturatedhydrocarbon group includes linear chain alkanediyl groups, branchedchain alkanediyl groups, monocyclic or polycyclic divalent saturatedhydrocarbon groups, and a group combining two or more of theabove-mentioned groups.

Specific examples of the divalent saturated hydrocarbon group includethose as referred to for L^(b1).

L^(b2) is preferably a single bond.

L^(b3) is preferably a C1-C4 alkanediyl group.

L^(b4) is preferably a C1-C8 divalent saturated hydrocarbon group wherea hydrogen atom may be replaced by a fluorine atom.

L^(b5) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group.

L^(b6) preferably a single bond or a C1-C4 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom.

L^(b7) is preferably a single bond or a C1-C18 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or carbonyl group.

Among them, those of formulae (b1-1) and (b1-2) are preferred. Examplesof the group represented by formula (b1-1) include those represented byformulae (b1-4), (b1-5), (b1-6), (b1-7) and (b1-8).

In formula (b1-4), L^(b8) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom or a hydroxyl group.

In formula (b1-5), L^(b9) represents a C1-C20 divalent saturatedhydrocarbon group, and L^(b10) represents a single bond or a C1-C19divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, provided that the totalcarbon atoms of L^(b10) and L^(b9) is up to 20.

In formula (b1-6), L^(b11) represents a C1-C21 divalent saturatedhydrocarbon group, and L^(b12) represents a single bond or a C1-C20divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b11) and L^(b12) is up to 21.

In formula (b1-7), L^(b13) represents a C1-C19 divalent saturatedhydrocarbon group, L^(b14) represents a single bond or a C1-C18 divalentsaturated hydrocarbon group, and L^(b15) represents a single bond or aC1-C18 divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b13), L^(b14) and L^(b15) is up to 19.

In formula (b1-8), L^(b16) represents a C1-C18 divalent saturatedhydrocarbon group, L^(b17) represents a C1-C18 divalent saturatedhydrocarbon group, and L^(b18) represents a single bond or a C1-C17divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b16), L^(b17) and L^(b18) is up to 19.

In these formulae, * represents a binding position, * of the left siderepresents a binding position to —C(Q¹)(Q²)-, and * of the right siderepresents a binding position to Y.

In these formulae, the divalent saturated hydrocarbon group includeslinear chain alkanediyl groups, branched chain alkanediyl groups,monocyclic or polycyclic divalent saturated hydrocarbon groups, and agroup combining two or more of the above-mentioned groups. Specificexamples of the divalent saturated hydrocarbon group include those asreferred to for L^(b1).

L^(b8) is preferably a C1-C4 alkanediyl group.

L^(b9) is preferably a C1-C8 divalent saturated hydrocarbon group.

L^(b10) is preferably a single bond or a C1-C19 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C8 divalentsaturated hydrocarbon group.

L^(b11) is preferably a C1-C8 divalent saturated hydrocarbon group.

L^(b12) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group.

L^(b13) is preferably a C1-C12 divalent saturated hydrocarbon group.

L^(b14) is preferably a single bond or a C1-C6 divalent saturatedhydrocarbon group.

L^(b15) is preferably a single bond or a C1-C18 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C8 divalentsaturated hydrocarbon group.

L^(b16) is preferably a C1-C12 divalent saturated hydrocarbon group.

L^(b17) is preferably a C1-C6 divalent saturated hydrocarbon group.

L^(b18) is preferably a single bond or a C1-C17 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C4 divalentsaturated hydrocarbon group.

Examples of the group represented by formula (b1-3) include thoserepresented by formulae (b1-9), (b1-10) and (b1-11).

In formula (b1-9), L^(b19) represents a single bond or a C1-C23 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, and L^(b20) represents a single bond or a C1-C23 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by ahydroxyl group or a fluorine atom and where a methylene group may bereplaced by an oxygen atom or carbonyl group, provided that the totalcarbon atoms of L^(b19) and L^(b20) is up to 23. In formula (b1-10),L^(b21) represents a single bond or a C1-C21 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, L^(b22) represents a single bond or a C1-C21 divalent saturatedhydrocarbon group and L^(b23) represents a single bond or a C1-C21divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom and where a methylenegroup may be replaced by an oxygen atom or a carbonyl group, providedthat the total carbon atoms of L^(b21), L^(b22) and L^(b23) is up to 21.

In formula (b1-11), L^(b24) represents a single bond or a C1-C21divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a fluorine atom, L^(b25) represents a single bond or aC1-C21 divalent saturated hydrocarbon group, and L^(b26) represents asingle bond or a C1-C20 divalent saturated hydrocarbon group where ahydrogen atom may be replaced by a hydroxyl group or a fluorine atom andwhere a methylene group may be replaced by an oxygen atom or a carbonylgroup, provided that the total carbon atoms of L^(b24), L^(b25) andL^(b26) is up to 21.

In these formulae, * represents a binding position to Y.

In these formulae, the divalent saturated hydrocarbon group includeslinear chain alkanediyl groups, branched chain alkanediyl groups,monocyclic or polycyclic divalent saturated hydrocarbon groups, and agroup combining two or more of the above-mentioned groups. Specificexamples of the divalent saturated hydrocarbon group include those asreferred to for L^(b1).

Examples of the divalent saturated hydrocarbon group where a methylenegroup has been replaced by an oxygen atom or a carbonyl group includethose having an acyloxy group where a hydrogen atom may be replaced by ahydroxyl group and where a methylene group may be replaced by an oxygenatom or a carbonyl group.

Examples of acyloxy group include an acetyloxy group, a propyonyloxygroup, a butyryloxy group, a cyclohexylcarbonyloxy group and anadamantylcarbonyloxy group.

Examples of acyloxy group where a hydrogen atom has been replaced by ahydroxyl group or where a methylene group has been replaced by an oxygenatom or a carbonyl group include an oxoadamantylcarbonyloxy group, ahydroxyadamantylcarbonyloxy group, an oxocyclohexylcarbonyloxy group,and a hydroxycyclohexylcarbonyloxy group.

Examples of the group represented by formula (b1-4) include thefollowing ones.

Examples of the group represented by formula (b1-5) include thefollowing ones.

Examples of the group represented by formula (b1-6) include thefollowing ones.

Examples of the group represented by formula (b1-7) include thefollowing ones.

Examples of the group represented by formula (b1-8) include thefollowing ones.

Examples of the group represented by formula (b1-2) include thefollowing ones.

Examples of the group represented by formula (b1-9) include thefollowing ones.

Examples of the group represented by formula (b1-10) include thefollowing ones.

Examples of the group represented by formula (b1-11) include thefollowing ones.

Preferred examples of the alicyclic hydrocarbon group represented by Yinclude those represented by the formula (Y1), the formula (Y2), theformula (Y3), the formula (Y4), the formula (Y5), the formula (Y6), theformula (Y7), the formula (Y8), the formula (Y9), the formula (Y10) andthe formula (Y11).

When a methylene group has been replaced by an oxygen atom, a sulfonylgroup or a carbonyl group in the alicyclic hydrocarbon group representedby Y, preferred examples of Y include those represented by the formula(Y12), the formula (Y13), the formula (Y14), the formula (Y15), theformula (Y16), the formula (Y17), the formula (Y18), the formula (Y19),the formula (Y20), the formula (Y21), the formula (Y22), the formula(Y23), the formula (Y24), the formula (Y25), the formula (Y26) and theformula (Y27).

Among the groups represented by the formula (Y1) to the formula (Y27),preferred are those represented by formulae (Y1) to (Y19); morepreferred are those represented by the formulae (Y11), (Y14), (Y15) and(Y19); and still more preferred are those represented by the formulae(Y11) and (Y14).

Substituents of the methyl group represented by Y and the alicyclichydrocarbon groups represented by Y include a halogen atom, a C1-C12alkyl group, a hydroxyl group, a C1-C12 hydroxyl-containing alkyl group,a C1-C12 alkoxy group, a C3-C16 alicyclic hydrocarbon group, a C6-C18aromatic hydrocarbon group, a C7-C21 aralkyl group, a C2-C4 acyl group,a glycidyloxy group, and —(CH₂)_(jb2)—O—CO—R^(b1)— in which R^(b1) is aC1-C16 alkyl group, C3-C16 alicyclic hydrocarbon group or C6-C18aromatic hydrocarbon group and jb2 is an integer of 0 to 2. Each of thealkyl group, the alicyclic hydrocarbon group, the aromatic hydrocarbongroup and the aralkyl group, which is the substituent for the alicyclichydrocarbon groups represented by Y may have a substituent such as analkyl group, a halogen atom or a hydroxyl group.

Examples of hydroxyl-containing alkyl group include a hydroxymethylgroup and a hydroxyethyl group.

Examples of the C1-C12 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxygroup, a heptyloxy group, an octyloxy group, a decyloxy group and adodecyloxy group.

Examples of the aromatic hydrocarbon group include an aryl group such asa phenyl group, a naphthyl group, an anthryl group, a p-methylphenylgroup, a p-tert-butylphenyl group, a p-adamantylphenyl group, a tolylgroup, a xylyl group, a cumyl group, a mesityl group, a biphenyl group,a phenanthryl group, a 2,6-diethylphenyl group and a2-methyl-6-ethylphenyl group.

Examples of the aralkyl group include a benzyl group, phenylpropylgroup, a phenethyl group, a naphthylmethyl group, or a naphthylethylgroup.

Examples of the acyl group include an acetyl group, a propyonyl groupand a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

For Y, specific examples of the alicyclic hydrocarbon group in which ahydrogen atom has been replaced by a substituent include the groups asfollow.

where represents a binding position.Y represents preferably a C3-C18 alicyclic hydrocarbon group in which ahydrogen atom can be replaced by a substituent and in which a methylenegroup can be replaced by —O—, —CO₂— or —SO₂—, more preferably anamadantyl group in which a hydrogen atom can be replaced by asubstituent and in which a methylene group can be replaced by —O—, —CO₂—or —SO₂—, and still more preferably an amadantyl group, ahydroxyamadantyl group or an oxoamadantyl group.

Specific example of the anion represented by formula (I-A) include thoserepresented by formulae (I-A-1) to (I-A-31), preferably thoserepresented by formulae (I-A-1) to (I-A-29), more preferably thoserepresented by formulae (I-A-1) to (I-A-4), (I-A-9), (I-A-10), (I-A-24)to (I-A-29).

In formulae (I-A-1) to (I-A-31), Q¹ and Q² are as defined above; L⁴represents a single bond or a C1-C4 alkyl group, preferably a methylgroup; and R^(i2), R^(i3) and R^(i4) each independently represent aC1-C4 alkyl group.

Specific example of the anion represented by formula (I-A) include thoserepresented by formulae (Ia-1) to (Ia-11), more preferably thoserepresented by formulae (Ia-1) to (Ia-3) and (Ia-7) to (Ia-11), andfurther more preferably those represented by formulae (Ia-1), (Ia-2),(Ia-8) and (Ia-10).

Specific examples of the sulfoimide anion represented by Z⁻ includethose as follow.

Specific examples of the salt represented by formula (I) include thosewhich has an anion and a cation each as listed in Tables 1 and 2. In thetables, the symbols recited in each column represent the symbols of theabove-mentioned formula which represents the cation or anion shown inthe column. For example, The salt (I-1) represents the following one.

TABLE 1 Salt represented by formula (I) Z⁻ Cation (I-1) (Ia-2) (I-c-1)(I-2) (Ia-3) (I-c-1) (I-3) (Ia-7) (I-c-1) (I-4) (Ia-8) (I-c-1) (I-5)(Ia-10) (I-c-1) (I-6) (Ia-11) (I-c-1) (I-7) (Ia-2) (I-c-2) (I-8) (Ia-3)(I-c-2) (I-9) (Ia-7) (I-c-2) (I-10) (Ia-8) (I-c-2) (I-11) (Ia-10)(I-c-2) (I-12) (Ia-11) (I-c-2) (I-13) (Ia-2) (I-c-4) (I-14) (Ia-3)(I-c-4) (I-15) (Ia-7) (I-c-4) (I-16) (Ia-8) (I-c-4) (I-17) (Ia-10)(I-c-4) (I-18) (Ia-11) (I-c-4) (I-19) (Ia-2) (I-c-6) (I-20) (Ia-3)(I-c-6) (I-21) (Ia-7) (I-c-6) (I-22) (Ia-8) (I-c-6) (I-23) (Ia-10)(I-c-6) (I-24) (Ia-11) (I-c-6)

TABLE 2 Salt represented by formula (I) Z⁻ Cation (I-25) (Ia-2) (I-c-7)(I-26) (Ia-3) (I-c-7) (I-27) (Ia-7) (I-c-7) (I-28) (Ia-8) (I-c-7) (I-29)(Ia-10) (I-c-7) (I-30) (Ia-11) (I-c-7) (I-31) (Ia-2) (I-c-10) (I-32)(Ia-3) (I-c-10) (I-33) (Ia-7) (I-c-10) (I-34) (Ia-8) (I-c-10) (I-35)(Ia-10) (I-c-10) (I-36) (Ia-11) (I-c-10) (I-37) (Ia-2) (I-c-11) (I-38)(Ia-3) (I-c-11) (I-39) (Ia-7) (I-c-11) (I-40) (Ia-8) (I-c-11) (I-41)(Ia-10) (I-c-11) (I-42) (Ia-11) (I-c-11) (I-43) (Ia-2) (I-c-33) (I-44)(Ia-3) (I-c-33) (I-45) (Ia-7) (I-c-33) (I-46) (Ia-8) (I-c-33) (I-47)(Ia-10) (I-c-33) (I-48) (Ia-11) (I-c-33) (I-49) (Ia-2) (I-c-35) (I-50)(Ia-3) (I-c-35) (I-51) (Ia-7) (I-c-35) (I-52) (Ia-8) (I-c-35) (I-53)(Ia-10) (I-c-35) (I-54) (Ia-11) (I-c-35) (I-55) (Ia-2) (I-c-25) (I-56)(Ia-3) (I-c-25) (I-57) (Ia-7) (I-c-25) (I-58) (Ia-8) (I-c-25) (I-59)(Ia-10) (I-c-25) (I-60) (Ia-11) (I-c-25)

The salt represented by formula (I) is preferably Salt (I-1), Salt(I-2), Salt (I-4), Salt (I-5), Salt (I-13), Salt (I-14), Salt (I-16),Salt (I-17), Salt (I-19), Salt (I-20), Salt (I-22), Salt (I-23), Salt(I-31), Salt (I-32), Salt (I-34), Salt (I-35), Salt (I-43), Salt (I-44),Salt (I-46), Salt (I-47), Salt (I-49), Salt (I-50), Salt (I-52), Salt(I-53), Salt (I-55), Salt (I-56), Salt (I-58) and Salt (I-59), morepreferably Salt (I-1), Salt (I-2), Salt (I-4), Salt (I-5), Salt (I-13),Salt (I-14), Salt (I-16), Salt (I-17), Salt (I-19), Salt (I-20), Salt(I-22), Salt (I-23), Salt (I-31), Salt (I-32), Salt (I-34), Salt (I-35),Salt (I-49), Salt (I-50) and Salt (I-55), and still more preferably Salt(I-1), Salt (I-2), Salt (I-4), Salt (I-5), Salt (I-13), Salt (I-14),Salt (I-16), Salt (I-17), Salt (I-19), Salt (I-20), Salt (I-22), Salt(I-23), Salt (I-31), Salt (I-32), Salt (I-34) and Salt (I-35).

The compound represented by formula (I) can be produced by reacting thecompound of formula (I-a) and the compound of formula (I-b), in thepresence of a catalyst, in a solvent.

in which ⁺X, R¹, R², R³, Z and m are as defined above.

For the reaction, examples of the catalyst include an oxalic acid.

Examples of the solvent include chloroform and an ion-exchanged water.The reaction can be conducted at temperature of preferably 10° C. to 60°C., for 0.5 to 12 hours.

Examples of the compound of formula (I-b) include the following ones.

The compound of formula (I-b) is available on the market and can beprepared according to a method recited in Examples of JP2011-116747A1.

The compound of formula (I-a) can be prepared by reacting the compoundof formula (I-c) and the compound of formula (I-d), at the presence ofAgClO₄, in a solvent such as chloroform:

in which ⁺X, R¹, R², R³ and m are as defined above, and X represents asulfur atom or an iodine atom.

The reaction can be conducted at temperature of preferably 10° C. to 60°C., for 0.5 to 120 hours.

Examples of the compound of formula (I-c) include the following ones.

The compound of formulae (I-c) is available on the market and wasmanufactured by Tokyo Chemical Industries, Co., Ltd.

Examples of the compound of formula (I-d) include the following ones.

The compound of formula (I-d) is available on the market and wasmanufactured by Tokyo Chemical Industries, Co., Ltd.

In the photoresist composition of the disclosure, the amount of the saltrepresented by formula (I) is preferably 1 to 20 parts by weight, morepreferably 2 to 15 parts by weight, relative to 100 parts by weight ofthe resin having an acid-labile group.

The photoresist composition may further comprise an acid generator knownin the field of the photoresist compositions.

The acid generator generates an acid from the acid generator byexposure.

The acid generator includes a nonionic acid generator, an ionic acidgenerator and the combination thereof.

Examples of the nonionic acid generator include an organo-halogencompound, a sulfonate compound such as a 2-nitrobenzylsulfonate, anaromatic sulfonate, an oxime sulfonate, an N-sulfonyloxyimide, asulfonyloxyketone and diazonaphthoquinone 4-sulfonate, and a sulfonecompound such as a disulfone, a ketosulfone and a sulfonyldiazomethane.Examples of the ionic acid generator include an onium salt compound suchas a diazonium salt, a phosphonium salt, a sulfonium salt and aniodonium salt. Examples of the anion of the onium salt include asulfonic acid anion, a sulfonylimide anion and a sulfonylmethide anion.

Specific examples of the acid generator include acid generatorsdescribed in JP 63-26653 A, JP 55-164824 A, JP 62-69263 A, JP 63-146038A, JP63-163452 A, JP62-153853 A, JP63-146029 A, U.S. Pat. No. 3,779,778,U.S. Pat. No. 3,849,137, DE Pat. No. 3914407 and EP Patent No. 126,712.

The acid generator for the photoresist composition is preferably afluorine-containing acid generator.

Preferable examples of the acid generator include a salt which comprisesthe anion represented by formula (I-A) and either a sulfonium cation,specifically an arylsulfonium cation, or an iodonium cation.

Preferred examples of the organic cation include the organic cationsrepresented by the formulae (b2-1), (b2-2), (b2-3) and (b2-4)

In the formulae (b2-1) to (b2-4), R^(b4), R^(b5) and R^(b6)independently represent a C1-C30 aliphatic hydrocarbon group, a C3-C36alicyclic hydrocarbon group and a C6-C36 aromatic hydrocarbon group.

The aliphatic hydrocarbon group can have a substituent selected from thegroup consisting of a hydroxy group, a C1-C12 alkoxy group, a C3-C12alicyclic hydrocarbon group and a C6-C18 aromatic hydrocarbon group. Thealicyclic hydrocarbon group can have a substituent selected from thegroup consisting of a C1-C18 aliphatic hydrocarbon group, a C2-C4 acylgroup and a glycidyloxy group. The aromatic hydrocarbon group can have asubstituent selected from the group consisting of a hydroxy group, aC1-C18 aliphatic hydrocarbon group and a C1-C12 alkoxy group.

R^(b4) and R^(b5) can be bonded to form a ring together with theadjacent S⁺, and a methylene group in the ring may be replaced by —CO—,—O— or —SO—.

R^(b7) and R^(b8) are independently in each occurrence a hydroxy group,a C1-C12 alkyl group or a C1-C12 alkoxy group, m2 and n2 independentlyrepresents an integer of 0 to 5.

R^(b9) and R^(b10) independently represent a C1-C36 aliphatichydrocarbon group or a C3-C36 alicyclic hydrocarbon group.

R^(b9) and R^(b10) can be bonded to form a ring together with theadjacent S⁺, and a methylene group in the divalent acyclic hydrocarbongroup may be replaced by —CO—, —O— or —SO—.

R^(b11) represents a hydrogen atom, a C1-C36 aliphatic hydrocarbongroup, a C3-C36 alicyclic hydrocarbon group or a C6-C18 aromatichydrocarbon group.

R^(b12) represents a C1-C12 aliphatic hydrocarbon group in which ahydrogen atom can be replaced by a C6-C18 aromatic hydrocarbon group, aC3-C18 saturated cyclic hydrocarbon group and a C6-C18 aromatichydrocarbon group in which a hydrogen atom can be replaced by a C1-C12alkoxy group or a (C1-C12 alkyl) carbonyloxy group.

R^(b11) and R^(b12) can be bonded each other to form a C1-C10 divalentacyclic hydrocarbon group which forms a 2-oxocycloalkyl group togetherwith the adjacent —CHCO—, and a methylene group in the divalent acyclichydrocarbon group may be replaced by —CO—, —O— or —SO—.

R^(b13), R^(b14), R^(b15), R^(b16), R^(b17) and R^(b18) independentlyrepresent a hydroxy group, a C1-C12 aliphatic hydrocarbon group or aC1-C12 alkoxy group.

L^(b31) represents —S— or —O— and o2, p2, s2 and t2 each independentlyrepresents an integer of 0 to 5, q2 and r2 each independently representsan integer of 0 to 4, and u2 represents 0 or 1.

Preferred examples of the aliphatic hydrocarbon group represented byR^(b4) to R^(b12) include an alkyl group such as a methyl group, anethyl group, a propyl group, an isopropyl group, a butyl group, asec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, anoctyl group and a 2-ethylhexyl group. The aliphatic hydrocarbon grouprepresented by R^(b9), R^(b10), R^(b11) and R^(b12) has preferably 1 to12 carbon atoms, more preferably 4 to 12 carbon atoms.

The alicyclic hydrocarbon group may be monocyclic or polycyclic.Preferred examples thereof include a cycloalkyl group such as acyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, adimethylcyclohexyl group, a cycloheptyl group and a cyclooctyl group, agroup obtained by hydrogenating a condensed aromatic hydrocarbon groupsuch as a hydronaphthyl group, a bridged cyclic hydrocarbon group suchas an adamantyl group, a norbornyl group and a decahydronaphtyl group,and the following groups.

The alicyclic hydrocarbon group represented by R^(b9), R^(b10), R^(b11)and R^(b12) has preferably 3 to 18 carbon atoms, more preferably 4 to 12carbon atoms.

Examples of the alicyclic hydrocarbon group in which a hydrogen atom hasbeen replaced by an aliphatic hydrocarbon group include amethylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornylgroup, and an isonorbornyl group.

The alicyclic hydrocarbon group in which a hydrogen atom has beenreplaced by an aliphatic hydrocarbon group has preferably 20 or lesscarbon atoms in total.

Examples of the aromatic hydrocarbon group include an aryl group such asa phenyl group, tolyl group, xylyl group, cumenyl group, mesityl group,p-ethylphenyl group, p-tert-butylphenyl group, p-adamantylphenyl group,a biphenylyl group, a naphthyl group, a phenanthryl group, a2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group.

When the aromatic hydrocarbon group has an alicyclic hydrocarbon groupor an aliphatic hydrocarbon group, it is preferred that the alicyclichydrocarbon group and the aliphatic hydrocarbon group have respectively1 to 18 carbon atoms and 3 to 18 carbon atoms.

Examples of the aromatic hydrocarbon group in which a hydrogen atom hasbeen replaced by an alkoxy group include p-methoxyphenyl group.

Examples of the aliphatic hydrocarbon group in which a hydrogen atom hasbeen replaced by an aromatic hydrocarbon group include a benzyl group, aphenethyl group, a phenylpropyl group, trityl group, naphthylmethylgroup, and a naphthylethyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the acyl group include an acetyl group, a propyonyl groupand a butyryl group.

Examples of alkylcarbonyloxy group include a methylcarbonyloxy group, anethylcarbonyloxy group, a n-propylcarbonyloxy group, anisopropylcarbonyloxy group, a n-butylcarbonyloxy group, asec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, apentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxygroup and a 2-ethyl hexylcarbonyloxy group.

The ring group formed by bonding R^(b4) and R^(b5) together with theadjacent S⁺ may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring is generally a 3 to 12-membered,preferably 3 to 7-membered one. Examples of the ring include thefollowing ones.

The ring group formed by bonding R^(b9) and R^(b10) together with theadjacent S⁺ may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring has generally C3-C12, preferablyC3-C7 carbon atoms. Examples of the ring include a thiolan-1-ium ring(tetrahydrothiphenium ring), a thian-1-ium ring and a 1,4-oxathian-4-iumring.

The ring group formed by bonding R^(b11) and R^(b12) together with—CH—CO— may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring has generally C3-C12, preferablyC3-C7 carbon atoms. Examples of the ring include an oxocycloheptanering, an oxocyclohexane ring, an oxonorbornane ring, and anoxoadamantane ring.

Preferred examples of the cation for Salt (a) include an arylsulfoniumcation, specifically a cation of formula (b2-1), and more specifically aphenylsulfonium cation.

Specific examples of the acid generator include the following saltsrepresented by formulae (B1-1) to (B1-30). Among them, the saltsrepresented by formulae (B1-1), (B1-2), (B1-3), (B1-6), (B1-7), (B1-11),(B1-12), (B1-13), (B1-14), (B1-20), (B1-21), (B1-22), (B1-23), (B1-24),(B1-27) and (B1-28) are preferred, and the salts represented by formulae(B1-1), (B1-2), (B1-3), (B1-5), (B1-6), (B1-7), (B1-11), (B1-12),(B1-13), (B1-14), (B1-20), (B1-21), (B1-22), (B1-23) and (B1-24) aremore preferred.

The photoresist composition of the disclosure may comprise two or moreacid generators known in the art.

When the photoresist composition comprises the acid generator, thecontent of the acid generator is preferably 1 to 20 parts by mass, morepreferably 3 to 15 parts by mass, relative to 100 parts by mass of theresin having an acid-labile group.

When the photoresist composition comprises the acid generator, the totalamount of the salt represented by formula (I) and the acid generator ispreferably 1.5 to 40 parts by mass, more preferably 3 to 35 parts bymass, relative to 100 parts by mass of the resin having an acid-labilegroup.

The content ratio of the salt represented by formula (I) and the acidgenerator, which is represented by [the amount of the salt representedby formula (I): the acid generator, mass basis] is preferably 1:99 to100:0, and more preferably 1:9 to 9:1.

<Resin (A)>

The resin having an acid-labile group, which is sometimes referred to as“Resin (A)”, usually comprises a structural unit having an acid-labilegroup and no fluorine atom. Hereinafter, the structural unit issometimes referred to as “structural unit (a1)”.

Preferably Resin (A) further comprises another structural unit than thestructural unit (a1), i.e. a structural unit having no acid-labilegroup, which is sometimes referred to as “structural unit (s)”.

The structural unit (a1) is derived from a compound having anacid-labile group which compound is sometimes referred to as “Monomer(a1)”.

Herein, “an acid-labile group” means a group which has a hydrophilicgroup, such as a hydroxy group or a carboxy group, resulting fromremoving a leaving group therefrom by the action of an acid.

For Resin (A), the acid-labile groups represented by formulae (1) and(2) are preferred:

In formula (1), R^(a1), R^(a2) and R^(a3) independently each represent aC1-C8 alkyl group, a C3-C20 alicyclic hydrocarbon group or a groupconsisting of them, and R^(a1) and R^(a2) can be bonded each other toform a C2-C20 divalent hydrocarbon group, na represents an integer of 0or 1, and * represents a binding site.

In formula (2), R^(a1′) and R^(a2′) independently each represent ahydrogen atom or a C1-C12 hydrocarbon group, and R^(a3′) represents aC1-C20 hydrocarbon group, and R^(a2′) and R^(a3′) can be bonded eachother to form a C2-C20 divalent hydrocarbon group, and one or more —CH₂—in the hydrocarbon group and the divalent hydrocarbon group can bereplaced by —O— or —S—, X represents an oxygen atom or a sulfur atom,and represents a binding site.

For R^(a1), R^(a2) and R^(a3), specific examples of the alkyl groupinclude a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group andan octyl group.

The alicyclic hydrocarbon group may be monocyclic or polycyclic.

Examples of the alicyclic hydrocarbon group include a monocyclicalicyclic hydrocarbon group such as a C3-C20 cycloalkyl group (e.g. acyclopentyl group, a cyclohexyl group, a cycloheptyl group and acyclooctyl group) and a polycyclic alicyclic hydrocarbon group such as adecahydronaphthyl group, an adamantyl group, a norbornyl group, and thefollowings:

in which * represents a binding site.

The alicyclic hydrocarbon group preferably has 3 to 16 carbon atoms.

Examples of the group consisting of alkyl and alicyclic hydrocarbongroup include a methylcyclohexyl group, a dimethylcyclohexyl group, amethylnorbornyl group, an adamantylmethyl group, and a norbornylethylgroup.

The “na” is preferably 0.

When the divalent hydrocarbon group is formed by bonding R^(a1) andR^(a2) each other, examples of the moiety —C(R^(a1))(R^(a2))(R^(a3))include the following groups and the divalent hydrocarbon grouppreferably has 3 to 12 carbon atoms.

wherein R^(a3) is the same as defined above and * represents a bindingsite.

The group represented by formula (1) wherein R^(a1), R^(a2) and R^(a3)independently each represent a C1-C8 alkyl group such as a tert-butylgroup, the group represented by formula (1) wherein R^(a1) and R^(a2)are bonded each other to form an adamantyl ring and R^(a3) is a C1-C8alkyl group such as a2-alkyl-2-adamantyl group, and the grouprepresented by formula (1) wherein R^(a1) and R^(a2) are C1-C8 alkylgroups and R^(a3) is an adamantyl group such as a1-(1-adamantyl)-1-alkylalkoxycarbonyl group are preferred.

For formula (2), examples of the hydrocarbon group include an alkylgroup, an alicyclic hydrocarbon group, an aromatic hydrocarbon group anda group consisting of two or more of them.

Examples of the aliphatic hydrocarbon group and the alicyclichydrocarbon group include the same as described above. Examples of thearomatic hydrocarbon group include an aryl group such as a phenyl group,a naphthyl group, a p-methylphenyl group, a p-tert-butylphenyl group, ap-adamantylphenyl group, a tolyl group, a xylyl group, a cumyl group, amesityl group, a biphenyl group, an anthryl group, a phenanthryl group,a 2,6-diethylphenyl group and a 2-methyl-6-ethylphenyl group.

Examples of the divalent hydrocarbon group formed by bonding R^(a2′) andR^(a3′) each other include those formed by removing a hydrogen atom fromthe hydrocarbon group represented by R^(a1′), R^(a2′) and R^(a3′).

It is preferred that at least one of R^(a1′) and R^(a2′) is a hydrogenatom.

Examples of the group represented by formula (2) include the following.

Monomer (a1) is preferably a monomer having an acid-labile group in itsside chain and an ethylenic unsaturated group, more preferably a(meth)acrylate monomer having an acid-labile group in its side chain,and still more preferably a (meth)acrylate monomer having the grouprepresented by formula (1) or (2).

The (meth)acrylate monomer having an acid-labile group in its side chainis preferably those which comprise a C5-C20 alicyclic hydrocarbon group.The resin which comprises a structural unit derived from such monomerscan provide improved resolution for a photoresist pattern to be preparedtherefrom.

The structural unit derived from a (meth)acrylate monomer having thegroup represented by formula (1) is preferably one of structural unitsrepresented by formulae (a1-0), (a1-1) and (a1-2).

In each formula, L^(a01), L^(a1) and L^(a2) each independently represent—O— or *—O—(CH₂)_(k1)—CO—O— in which k1 represents an integer of 1 to 7and represents a binding site to —CO—,

R^(a01), R^(a4) and R^(a5) each independently represent a hydrogen atomor a methyl group,R^(a02), R^(a03), R^(a04), R^(a6) and R^(a7) each independentlyrepresent a C1-C8 alkyl group, a C3-C18 alicyclic hydrocarbon group, ora group formed by combining them,m1 represents an integer of 0 to 14,n1 represents an integer of 0 to 10, andn1′ represents an integer of 0 to 3.

Hereinafter, the structural units represented by formulae (a1-0), (a1-1)and (a1-2) are respectively referred to as “structural unit (a1-0)”,“structural unit (a1-1)” and “structural unit (a1-2)”. Resin (A) maycomprise two or more of such structural units.

L^(a01) is preferably *—O— or *—O—(CH₂)_(f1)—CO—O— in which * representsa binding site to —CO—, and f1 represents an integer of 1 to 4, and ismore preferably *—O— or *—O—CH₂—CO—O—, and is especially preferably*—O—.

R^(a01) is preferably a methyl group.

For R^(a02), R^(a03) and R^(a04), examples of the alkyl group, thealicyclic hydrocarbon group and the group formed by combining theminclude the same as referred for R^(a1), R^(a2) and R^(a3).

The alkyl group preferably has 1 to 6 carbon atoms.

The alicyclic hydrocarbon group preferably has 3 to 8 carbon atoms andmore preferably 3 to 6 carbon atoms. The alicyclic hydrocarbon group ispreferably a saturated aliphatic cyclic hydrocarbon group.

The group formed by combining them preferably has 18 carbon atoms orless in total, examples of which include a methylcyclohexyl group, adimethylcyclohexyl group, and a methylnorbornyl group. Each of R^(a02)and R^(a03) is preferably a C1-C6 alkyl group, more preferably a methylgroup and an ethyl group.

R^(a04) is preferably a C1-C6 alkyl group and a C5-C12 alicyclichydrocarbon group, more preferably a methyl group, an ethyl group, acyclohexyl group, and an adamantyl group.

Each of L^(a1) and L^(a2) is preferably *—O— or *—O—(CH₂)_(f1)—CO—O— inwhich * represents a binding site to —CO—, and f1 is the same as definedabove, and is more preferably *—O— or *—O—CH₂—CO—O—, and is especiallypreferably *—O—.

Each of R^(a4) and R^(a5) is preferably a methyl group.

For R^(a6) and R^(a7), examples of the alkyl group include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a tert-butyl group, a pentyl group, a heptyl group, a2-ethylheptyl group and an octyl group.

For R^(a6) and R^(a7), examples of the alicyclic hydrocarbon groupinclude a monocyclic alicyclic hydrocarbon group such as a cyclohexylgroup, a methylcyclohexyl group, a dimethylcyclohexyl group, acycloheptyl group and a methylcycloheptyl group, and a polycyclicalicyclic hydrocarbon group such as a decahydronaphthyl group, anadamantyl group, a norbornyl group, a methylnorbornyl group and thefollowing. For R^(a6) and R^(a7), examples of the group consisting of analkyl group and an alicyclic hydrocarbon group include an aralkyl groupsuch as a benzyl group, and a phenethyl group.

The alkyl group represented by R^(a6) and R^(a7) is preferably a C1-C6alkyl group.

The alicyclic hydrocarbon group represented by R^(a6) and R^(a7) ispreferably a C3-C8 alicyclic hydrocarbon group, more preferably a C3-C6alicyclic hydrocarbon group.

The “m1” is preferably an integer of 0 to 3, and is more preferably 0 or1.

The “n1” is preferably an integer of 0 to 3, and is more preferably 0 or1.

The “n1′” is preferably 0 or 1.

Examples of the structural unit (a1-0) include those represented byformulae (a1-0-1) to (a1-0-12), preferably those represented by formulae(a1-0-1) to (a1-0-10).

Examples of the structural unit (a1-0) further include such groups thata methyl group has been replaced by a hydrogen atom in any one offormulae (a1-0-1) to (a1-0-12).

Examples of the monomer from which the structural unit (a1-1) is derivedinclude the monomers described in JP2010-204646A1, and the followingmonomers represented by the formulae (a1-1-1) to (a1-1-8), preferablythe following monomers represented by the formulae (a1-1-1) to (a1-1-4).

Examples of the monomer from which the structural unit (a1-2) is derivedinclude 1-ethylcyclopentan-1-yl acrylate, 1-ethylcyclopentan-1-ylmethacrylate, 1-ethylcyclohexan-1-yl acrylate, 1-ethylcyclohexan-1-ylmethacrylate, 1-ethylcycloheptan-1-yl acrylate, 1-ethylcycloheptan-1-ylmethacrylate, 1-methylcyclopentan-1-yl acrylate,1-methylcyclopentan-1-yl methacrylate, 1-isopropylcyclopentan-1-ylacrylate and 1-isopropylcyclopentan-1-yl methacrylate, preferably themonomers represented by formulae (a1-2-1) to (a1-2-12), more preferablythe monomers represented by formulae (a1-2-3), (a1-2-4), (a1-2-9) and(a1-2-10), still more preferably the monomers represented by formulae(a1-2-3) and (a1-2-9).

The content of the structural unit having an acid-labile group in theresin is usually 10 to 95% by mole, preferably 15 to 90% by mole andmore preferably 20 to 85% by mole based on 100% by mole of all thestructural units of the resin. The content of the structural unit havingan acid-labile group in the resin can be adjusted by adjusting theamount of the monomer having an acid-labile group based on the totalamount of the monomers used for producing the resin.

When the resin comprises one or more of the structural units representedby formulae (a1-0), (a1-1) and (a1-2), the total content of thestructural units is usually 10 to 95% by mole, preferably 15 to 90% bymole and more preferably 15 to 90% by mole and still more preferably 20to 85% by mole based on 100% by mole of all the structural units of theresin.

Other examples of the structural unit (a1) having a group represented byformula (1) include a structural unit represented by formula (a1-3):

wherein R^(a9) represents a hydrogen atom, a carboxyl group, a cyanogroup, a C1-C3 aliphatic hydrocarbon group which can have a hydroxygroup, or a group represented by —COOR^(a13) group in which R^(a13)represents a C1-C8 alkyl group or a C3-C20 alicyclic hydrocarbon group,and a group composed of a C1-C8 aliphatic hydrocarbon group and a C3-C20alicyclic hydrocarbon group, and the aliphatic hydrocarbon group and thealicyclic hydrocarbon group can have a hydroxy group, and a methylene inthe alkyl group and the alicyclic hydrocarbon group can be replaced by—O— or —CO—,R^(a10), R^(a11) and R^(a12) each independently represent a C1-C12 alkylgroup or a C3-C20 alicyclic hydrocarbon group, and R^(a10) and R^(a11)can be bonded each other to form a C3-C20 ring together with the carbonatom to which R^(a10) and R^(a11) are bonded, and the alkyl group andthe alicyclic hydrocarbon group can have a hydroxy group, and amethylene group in alkyl group and the alicyclic hydrocarbon group canbe replaced by —O— or —CO—.

As R^(a9), examples of the alkyl group which can have a hydroxy groupinclude a methyl group, an ethyl group, a propyl group, a hydroxymethylgroup and a 2-hydroxyethyl group.

Examples of the aliphatic hydrocarbon group represented by R^(a13)include a methyl group, an ethyl group, a propyl group.

Examples of the alicylic hydrocarbon group represented by R^(a13)include a cyclopropyl group, a cyclobutyl group, an adamantyl group, anadamantylmethyl group, a 1-adamantyl-1-methylethyl group, a2-oxo-oxolan-3-yl group and a 2-oxo-oxolan-4-yl group.

Examples of the alkyl group represented by R^(a10), R^(a11) and R^(a12)include a methyl group, an ethyl group, n-propyl group, an isopropylgroup, n-butyl group, sec-butyl group, tert-butyl group, a pentyl group,a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group.

The alicylic hydrocarbon group represented by R^(a10), R^(a11) andR^(a12) which may be a monocyclic or polycyclic group. Examples of themonocyclic alicyclic hydrocarbon group include cycloalkyl groups such asa cyclopropyl group, a cyclobutyl group, a cyclopentyl group, acyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cycloheptylgroup, a cyclodecyl group. Examples of the polycyclic alicyclichydrocarbon group include a hydronaphthyl group, an adamantyl group, a2-alkyladamantane-2-yl group, a 1-(adamantane-1-yl)alkane-1-yl group, anorbornyl group, a methylnorbornyl group, and an isobornyl group.

When the divalent hydrocarbon group is formed by bonding R^(a10) andR^(a11), examples of —C(R^(a10))(R^(a11))(R^(a12)) include the followingones;

where R^(a12) is as defined above.

Examples of the monomer from which the structural unit represented byformula (a1-3) is derived include tert-butyl 5-norbornene-2-carboxylate,1-cyclohexyl-1-methylethyl 5-norbornene-2-carboxylate,1-methylcyclohexyl 5-norbornene-2-carboxylate, 2-methyl-2-adamantyl5-norbornene-2-carboxylate, 2-ethyl-2-adamantyl5-norbornene-2-carboxylate, 1-(4-methylcyclohexyl)-1-methylethyl5-norbornene-2-carboxylate, 1-(4-hydroxycyclohexyl)-1-methylethyl5-norbornene-2-carboxylate, 1-methyl-1-(4-oxocyclohexyl)ethyl5-norbornene-2-carboxylate and 1-(1-adamantyl)-1-methylethyl5-norbornene-2-carboxylate.

When the resin has a structural unit represented by formula (a1-3), thephotoresist composition having excellent resolution and higherdry-etching resistance tends to be obtained.

When Resin (A) comprises the structural unit represented by formula(a1-3), the content of the structural unit is usually 10 to 95% by moleand preferably 15 to 90% by mole and more preferably 20 to 85% by molebased on total molar of all the structural units of the resin.

Other examples of the structural unit (a1) having a group represented byformula (2) include one represented by formula (a1-4):

wherein R^(a32) represents a hydrogen atom, a halogen atom other than afluorine atom, a C1-C6 alkyl group or a C1-C6 halogenated alkyl group,R^(a33) is independently in each occurrence a halogen atom other than afluorine atom, a hydroxy group, a C1-C6 alkyl group, a C1-C6 alkoxygroup, a C2-C4 acyl group, a C2-C4 acyloxy group, an acryloyl group or amethacryloyl group, 1^(a) represents an integer of 0 to 4,

R^(a34) and R^(a35) each independently represent a hydrogen atom or aC1-C12 hydrocarbon group, R^(a36) represents a C1-C20 aliphatichydrocarbon group in which a methylene group can be replaced by —O— or—S—, and R^(a35) and R^(a36) are bonded to each other to jointlyrepresent a C2-C20 divalent hydrocarbon group in which a methylene groupcan be replaced by —O— or —S—.

Examples of the alkyl group represented by R^(a32) and R^(a33) include amethyl group, an ethyl group, a propyl group, a butyl group, a pentylgroup, and a hexyl group, preferably a C1-C4 alkyl group, morepreferably a methyl group and an ethyl group, and still more preferablya methyl group.

Examples of the alkoxy group represented by R^(a33) include a methoxygroup, an ethoxy group, a propoxy group, an isopropoxy group, a butoxygroup, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, apentyloxy group and a hexyloxy group. Examples of the acyl grouprepresented by R^(a33) include an acetyl group, a propyonyl group and abutyryl group, and examples of the acyloxy group represented by R^(a33)include an acetyloxy group, a propyonyloxy group and a butyryloxy group.

Examples of halogen atom represented by R^(a32) and R^(a33) include achlorine atom and a bromine atom.

Examples of the groups represented by R^(a34) and R^(a35) include thoseas referred to for R^(a1′) and R^(a2′).

Examples of the groups represented by R^(a36) include those as referredto for R^(a3′).

R^(a32) preferably represents a hydrogen atom.

R^(a33) is preferably a C1-C4 alkoxy group, more preferably a methoxygroup and an ethoxy group, and still more preferably a methoxy group.

The symbol “1a” preferably represents 0 or 1, more preferably 1.

R^(a34) preferably represents a hydrogen atom.

R^(a35) is preferably a C1-C12 monovalent hydrocarbon group, morepreferably a methyl group and an ethyl group.

The hydrocarbon group represented by R^(a36) includes a C1-C18 alkylgroup, a C3-C18 monovalent alicyclic hydrocarbon group, a C6-C18monovalent aromatic hydrocarbon group, and any combination of them, andpreferably a C1-C18 alkyl group, a C3-C18 monovalent alicyclichydrocarbon group and a C7-C18 aralkyl group. These groups may beunsubstituted or substituted. The alkyl group and the monovalentalicyclic hydrocarbon group are preferably unsubstituted. As thesubstituent for the monovalent aromatic hydrocarbon group, a C6-C10aryloxy group is preferred.

Examples of the monomer from which the structural unit (a1-4) is derivedinclude monomers recited in JP2010-204646A1. Among them, the monomersrepresented by formulae (a1-4-1), (a1-4-2), (a1-4-3), (a1-4-4),(a1-4-5), (a1-4-6) and (a1-4-7) are preferred, and the monomersrepresented by formulae (a1-4-1), (a1-4-2), (a1-4-3), (a1-4-4) and(a1-4-5) are more preferred.

When Resin (A) comprises a structural unit represented by formula(a1-4), its content is usually 10 to 95% by mole, preferably 15 to 90%by mole and more preferably 20 to 85% by mole based on 100% by mole ofall the structural units of the resin.

Other examples of the structural unit having an acid-labile groupinclude one represented by formula (a1-5):

In formula (1-5), R^(a8) represents a hydrogen atom, a halogen atomother than a fluorine atom, or a C1-C6 alkyl group which may have ahalogen atom other than a fluorine atom,

R^(a1), represents a single bond or *—(CH₂)_(h3)—CO-L⁵⁴- in which k1represents an integer of 1 to 4 and represents a binding site to L⁵⁴,L⁵¹, L⁵², L⁵³ and L⁵⁴ each independently represent an oxygen atom or asulfur atom,s1 represents an integer of 1 to 3, and s1′ represents an integer of 0to 3.

Herein, the structural unit represented by formula (a1-5) is sometimesreferred to as “structural unit (a1-5)”.

Examples of halogen atoms include a chlorine atom.

Examples of the alkyl group include a methyl group, an ethyl group,n-propyl group, an isopropyl group, n-butyl group, sec-butyl group,tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a2-ethylhexyl group, and an octyl group.

In the formula (a1-5), R^(a8) preferably represents a hydrogen atom, ora methyl group.

L⁵¹ represents preferably an oxygen atom.

It is preferred that one of L⁵² and L⁵³ represents an oxygen atom, whilethe other represents a sulfur atom.

s1 preferably represents 1. s1′ represents an integer of 0 to 2.

Z^(a1) preferably represents a single bond or *—CH₂—CO—O— wherein *represents a binding site to L⁵¹.

Examples of the monomer from which the structural unit (a1-5) is derivedinclude one mentioned in JP2010-61117A1 and the following ones:

When Resin (A) comprises a structural unit (a1-5), its content isusually 1 to 50% by mole, preferably 3 to 45% by mole and morepreferably 5 to 40% by mole based on 100% by mole of all the structuralunits of the resin.

Resin (A) comprises preferably one or more of the structural units(a1-0), (a1-1), (a1-2) and (a1-5), more preferably at least one of thestructural units (a1-1), (a1-2) and (a1-5), still more preferably two ormore of the structural units (a1-1), (a1-2) and (a1-5), and further morepreferably the structural units (a1-1) and (a1-2) or the structuralunits (a1-1) and (a1-5).

Resin (A) comprises preferably the structural unit (a-1).

The structural unit (s) is derived from a monomer having no acid-labilegroup.

As to the monomer having no acid-labile group, monomers which have beenknown to in the art can be used as such monomer, and they are notlimited to any specific one provided that it has no acid-labile group.

The structural unit having no acid-labile group preferably has a hydroxygroup or a lactone ring. When the resin comprises the structural unitderived from the monomer having no acid-labile group and having ahydroxy group or a lactone ring, a photoresist composition capable ofproviding a photoresist film with good resolution and adhesiveness ofphotoresist to a substrate can be obtained.

Hereinafter, the structural unit having no acid-labile group and havinga hydroxy group is referred to as “structural unit (a2)”, and thestructural unit having no acid-labile group and having a lactone ring isreferred to as “structural unit (a3)”.

The hydroxy group which the structural unit (a2) has may be an alcoholichydroxy group or a phenolic hydroxy group.

When KrF excimer laser (wavelength: 248 nm) lithography system, or ahigh energy laser such as electron beam and extreme ultraviolet is usedas an exposure system, the resin which comprises the structural unit(a2) having a phenolic hydroxy group is preferred. When ArF excimerlaser (wavelength: 193 nm) is used as an exposure system, the resinwhich comprises the structural unit (a2) having an alcoholic hydroxygroup is preferred and the resin which comprises the structural unit(a2-1) described later is more preferred.

Resin (A) may comprise one or more of the structural units (a2).

Examples of the structural unit (a2) having a phenolic hydroxy groupinclude one represented by formula (a2-0):

In formula (a2-0), R^(a30) represents a hydrogen atom, a halogen atom,or a C1-C6 alkyl group, R^(a31) is independently in each occurrence ahalogen atom, a hydroxy group, a C1-C6 alkyl group, a C1-C6 alkoxygroup, a C2-C4 acyl group, a C2-C4 acyloxy group, an acryloyl group or amethacryloyl group, ma represents an integer of 0 to 4.

In the formula (a2-0), examples of the halogen atom include a chlorineatom, a bromine atom or iodine atom, examples of the C1-C6 alkyl groupinclude a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, an isobutyl group, a sec-butyl group, a tert-butylgroup, a pentyl group and a hexyl group, and a C1-C4 alkyl group ispreferred and a C1-C2 alkyl group is more preferred and a methyl groupis especially preferred. Examples of the C1-C6 alkoxy group include amethoxy group, an ethoxy group, a propoxy group, an isopropoxy group, abutoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxygroup, a pentyloxy group and a hexyloxy group, and a C1-C4 alkoxy groupis preferred and a C1-C2 alkoxy group is more preferred and a methoxygroup is especially preferred. Examples of the C2-C4 acyl group includean acetyl group, a propyonyl group and a butyryl group, and examples ofthe C2-C4 acyloxy group include an acetyloxy group, a propyonyloxy groupand a butyryloxy group. In the formula (a2-0), ma is preferably 0, 1 or2, and is more preferably 0 or 1, and especially preferably 0.

Among them, the structural units represented by formulae (a2-0-1),(a2-0-2), (a2-0-3) and (a2-0-4) are preferred as the structural unit(a2-0), and those represented by formulae (a2-0-1) and (a2-0-2) are morepreferred.

Resin (A) which comprises a structural unit represented by formula(a2-0) can be produced, for example, by polymerizing a monomer where itsphenolic hydroxy group has been protected with a suitable protectinggroup, followed by deprotection. Examples of the protecting group for aphenolic hydroxy group include an acetyl group.

When Resin (A) comprises the structural unit represented by formula(a2-0), its content is usually 5 to 95% by mole and preferably 10 to 80%by mole and more preferably 15 to 80% by mole based on total molar ofall the structural units of the resin.

Examples of the structural unit (a2) having an alcoholic hydroxy groupinclude one represented by formula (a2-1):

wherein R^(a14) represents a hydrogen atom or a methyl group, R^(a15)and R^(a16) each independently represent a hydrogen atom, a methyl groupor a hydroxy group, L^(a3) represents *—O— or *—O—(CH₂)_(k2)—CO—O— inwhich * represents a binding site to —CO—, and k2 represents an integerof 1 to 7, and of represents an integer of 0 to 10.

Hereinafter, the structural unit represented by formula (a2-1) isreferred to as “structural unit (a2-1)”.

In the formula (a2-1), R^(a14) is preferably a methyl group. R^(a15) ispreferably a hydrogen atom. R^(a16) is preferably a hydrogen atom or ahydroxy group. L^(a3) is preferably *—O— or *—O—(CH₂)_(f2)—CO—O— inwhich * represents a binding site to —CO—, and f2 represents an integerof 1 to 4, is more preferably *—O— and *—O—CH₂—CO—O—, and is still morepreferably *—O—, and of is preferably 0, 1, 2 or 3 and is morepreferably 0 or 1.

Examples of monomers from which the structural unit (a2-1) is derivedinclude compounds mentioned in JP2010-204646A.

Preferred examples of the structural unit (a2-1) include thoserepresented by formulae (a2-1-1) to (a2-1-6).

Among them, more preferred are the structural units represented byformulae (a2-1-1), (a2-1-2), (a2-1-3) and (a2-1-4), still more preferredare the structural units represented by formulae (a2-1-1) and (a2-1-3).

When Resin (A) comprises the structural unit (a2-1), its content isusually 1 to 45% by mole, preferably 1 to 40% by mole, and morepreferably 1 to 35% by mole, and especially preferably 2 to 20% by mole,based on total molar of all the structural units of the resin.

Examples of the lactone ring of the structural unit (a3) include amonocyclic lactone ring such as β-propiolactone ring, γ-butyrolactonering and γ-valerolactone ring, and a condensed ring formed from amonocyclic lactone ring and the other ring. Among them, preferred areγ-butyrolactone ring, an adamantanelactone ring and a condensed lactonering formed from γ-butyrolactone ring and the other ring.

Preferred examples of the structural unit (a3) include those representedby formulae (a3-1), (a3-2), (a3-3) and (a3-4):

In formulae, L^(a4), L^(a5) and L^(a6) each independently represent *—O—or *—O—(CH₂)_(k3)—CO—O— in which * represents a binding site to —CO— andk3 represents an integer of 1 to 7,

R^(a18), R^(a19) and R^(a20) each independently represent a hydrogenatom or a methyl group,R^(a21) represents a C1-C4 monovalent aliphatic hydrocarbon group,R^(a22) and R^(a23) are independently in each occurrence a carboxylgroup, a cyano group or a C1-C4 monovalent aliphatic hydrocarbon group,R^(a24) each independently represent a hydrogen atom, a halogen atomother than a fluorine atom, or a C1-C6 alkyl group which may have ahalogen atom other than a fluorine atom,L^(a7) represents a single bond, *¹-L^(a8)-O—, *¹-L^(a8)-CO—O—,*¹-L^(a8)-CO—O-L^(a9)-CO—O— or *¹-L^(a8)-CO—O-L^(a9)-O— in which L^(a8)and L^(a9) each independently represent C1-C6 divalent alkanediyl group,*¹ represents a binding site to —O—,and p1 represents an integer of 0 to 5, q1 and r1 independently eachrepresent an integer of 0 to 3.

Examples of halogen atom represented by R^(a24) include a chlorine atom,a bromine atom and an iodine atom.

Examples of the alkyl group represented by R^(a24) include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group,and a hexyl group, preferably a C1-C4 alkyl group, and more preferably amethyl group and an ethyl group.

As to R^(a24), examples of the alkyl group which has an halogen atominclude a trichloromethyl group, a tribromomethyl group, and atriiodomethyl group.

As to L^(a8) and L^(a9), examples of the alkanediyl group include amethylene group, an ethylene group, a propane-1,3-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group and a hexane-1,6-diylgroup, a butane-1,3-diyl group, 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

It is preferred that L^(a4), L^(a5) and L^(a6) each independentlyrepresent *—O— or *—O—(CH₂)_(d1)—CO—O— in which * represents a bindingsite to —CO— and d1 represents an integer of 1 to 4, and it is morepreferred that L^(a4), L^(a5) and L^(a6) are *—O— and *—O—CH₂—CO—O—, andit is still more preferred that L^(a4), L^(a5) and L^(a6) are *—O—.

R^(a18), R^(a19) and R^(a20) are preferably methyl groups. R^(a21) ispreferably a methyl group. It is preferred that R^(a22) and R^(a23) areindependently in each occurrence a carboxyl group, a cyano group or amethyl group.

It is preferred that p1, q1 and r1 each independently represent aninteger of 0 to 2, and it is more preferred that p1, q1 and r1 eachindependently represent 0 or 1.

R^(a24) is preferably a hydrogen atom or a C1-C4 alkyl group, morepreferably a hydrogen atom, a methyl group or an ethyl group, and stillmore preferably a hydrogen atom or a methyl group.

L^(a7) represents preferably a single bond or *¹-L^(a8)-CO—O—, morepreferably a single bond, *¹—CH₂—CO—O— or *¹—C₂H₄—CO—O—.

Examples of the structural unit (a3) include the following ones.

The structural unit (a3) is preferably one of formulae (a3-1-1) to(a3-1-4), formulae (a3-2-1) to (a3-2-4), formulae (a3-3-1) to (a3-3-4)and formulae (a3-4-1) to (a3-4-6), more preferably one of formulae(a3-1-1), formula (a3-1-2), formulae (a3-2-3) to (a3-2-4) and formulae(a3-4-1) to (a3-4-2), and still more preferably one of formulae(a3-1-1), (a3-4-1) and (a3-4-2).

Examples of the monomer from which the structural unit (a3) is derivedinclude those mentioned in US2010/203446A1, US2002/098441A1 andUS2013/143157A1.

When Resin (A) comprises the structural unit (a3), its content thereofis preferably 5 to 70% by mole, and more preferably 10 to 65% by moleand more preferably 10 to 60% by mole, based on total molar of all thestructural units of the resin.

Examples of another structural unit having no acid-labile group includea structural unit which has a hydrocarbon not being removed therefrom byaction of an acid.

Other examples of the structural unit having no acid-labile groupinclude one having an acid-stable hydrocarbon group.

Herein, the term “acid-stable hydrocarbon group” means such ahydrocarbon group that is not removed from the structural unit havingthe group by action of an acid generated from an acid generator asdescribed later.

The acid-stable hydrocarbon group may be a linear, branched or cyclichydrocarbon group.

The structural unit which has a hydrocarbon not being removed therefromby action of an acid may have a linear, branched or cyclic hydrocarbon,preferably an alicyclic hydrocarbon group.

Examples of the structural unit having an acid-stable hydrocarbon groupinclude one represented by formula (a5-1)

where R⁵¹ represents a hydrogen atom or a methyl group;R⁵² represents a C3-C18 monovalent alicyclic hydrocarbon group which mayhave a C1-C8 monovalent aliphatic hydrocarbon group as a substituent,provided that the alicyclic hydrocarbon group has no substituent on thecarbon atom bonded to L⁵¹; andL⁵¹ represents a single bond or a C1-C18 divalent saturated hydrocarbongroup where a methylene group can be replaced by an oxygen atom orcarbonyl group.

The alicyclic hydrocarbon group represented by R⁵² may be monocyclic orpolycyclic one.

Examples of the alicyclic hydrocarbon group include a monocyclichydrocarbon group such as a C3-C18 cycloalkyl group (e.g. a cyclopropylgroup, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group anda polycyclic alicyclic hydrocarbon group such as an adamantyl group, ora norbornyl group.

Examples of the aliphatic hydrocarbon group include an alkyl groups suchas a methyl group, an ethyl group, n-propyl group, isopropyl group,n-butyl group, sec-butyl group, tert-butyl group, a pentyl group, ahexyl group, an octyl group and 2-ethylhexyl group. Examples of thealicyclic hydrocarbon group having a substituent include a3-hydroxyadamantyl group, and a 3-methyladamantyl group. R⁵² ispreferably a C3-C18 unsubstituted alicyclic hydrocarbon group, morepreferably an adamantyl group, a norbornyl group or a cyclohexyl group.

Examples of the divalent saturated hydrocarbon group represented by L⁵¹include divalent aliphatic hydrocarbon groups and divalent alicyclichydrocarbon groups, preferably divalent aliphatic hydrocarbon groups.

Examples of divalent aliphatic hydrocarbon groups include alkanediylgroups such as a methylene group, an ethylene group, a propanediylgroup, a butanediyl group and a pentanediyl group.

The divalent alicyclic hydrocarbon groups may be monocyclic orpolycyclic one.

Examples of divalent monocyclic hydrocarbon groups includecycloalkanediyl groups such as a cyclopentanediyl group and acyclohexanediyl group. Examples of divalent polycyclic alicyclichydrocarbon groups include an adamantanediyl group and a norbornanediylgroup.

Examples of the divalent hydrocarbon group where a methylene group hasbeen replaced by an oxygen atom or carbonyl group include thoserepresented by formulae (L1-1) to (L1-4).

In these formulae, * represents a binding position to an oxygen atom.

X^(x1) is a carbonyloxy group or an oxycarbonyl group; and

L^(x1) is a C1-C16 divalent saturated hydrocarbon group, and L^(x2) is asingle bond or a C1-C15 divalent aliphatic saturated hydrocarbon group,provided that the total number of the carbon atoms in L^(x1) and L^(x2)is 16 or less.

L^(x3) is a C1-C17 divalent saturated hydrocarbon group, and L^(x4) is asingle bond or a C1-C16 divalent aliphatic saturated hydrocarbon group,provided that the total number of the carbon atoms in L^(x3) and L^(x4)is 17 or less.

L^(x5) is a C1-C15 divalent saturated hydrocarbon group, and L^(x6) andL^(x7) are a single bond or a C1-C14 divalent aliphatic saturatedhydrocarbon group, provided that the total number of the carbon atoms inL^(x5), L^(x6) and L^(x7) is 15 or less.

L^(x8) and L^(x9) are each independently a single bond or a C1-C12divalent aliphatic saturated hydrocarbon group, and W^(x1) is a C3-C15divalent cyclic saturated hydrocarbon group, provided that the totalnumber of the carbon atoms in L^(x8), L^(x9) and W^(x1) is 15 or less.

L^(x1) is preferably a C1-C8 divalent saturated hydrocarbon group, morepreferably a methylene group or an ethylene group.

L^(x2) is preferably a single bond, or a C1-C8 divalent saturatedhydrocarbon group, more preferably a single bond.

L^(x3) is preferably a C1-C8 divalent saturated hydrocarbon group, morepreferably a methylene group or an ethylene group.

L^(x4) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group, more preferably a single bond, a methylene group oran ethylene group.

L^(x5) is preferably a C1-C8 divalent saturated hydrocarbon group, morepreferably a methylene group or an ethylene group.

L^(x6) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group, more preferably a methylene group or an ethylenegroup.

L^(X7) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group, more preferably a methylene group or an ethylenegroup.

L^(x8) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group, more preferably a single bond or a methylene group.

L^(x9) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group, more preferably a single bond or a methylene group.

W^(x1) is a preferably C3-C10 divalent cyclic saturated hydrocarbongroup, more preferably a cyclohexanediyl group or an adamantanediylgroup.

Examples of the divalent hydrocarbon group represented by formula (L1-1)include the following ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the divalent hydrocarbon group represented by formula (L1-2)include the following ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the divalent hydrocarbon group represented by formula (L1-3)include the following ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the divalent hydrocarbon group represented by formula (L1-4)include the following ones.

In these formulae, * represents a binding position to an oxygen atom.

L⁵¹ is preferably a single bond or a group represented by formula(L1-1).

Examples of the structural unit represented by formula (a5-1) includethe following ones and those where a methyl group has been replaced by ahydrogen atom in each formula.

Resin (A) may further comprise another structural unit examples of whichinclude one known to skilled in the art.

Resin (A) comprises preferably the structural unit (a1) and thestructural unit (s), that is a copolymer of Monomer (a1) and a monomerfrom which the structural unit (s) is derived.

In Resin (A), the structural unit (a1) is one of the structural unit(a1-1) and the structural unit (a1-2) which preferably comprises acyclohexyl group or a cyclopentyl group. Preferably, Resin (A) comprisesthe structural unit (a1-1) and the structural unit (a1-2), or thestructural unit (a1-1) as the structural unit (a1).

The structural unit (s) is preferably one of the structural unit (a2)and the structural unit (a3). The structural unit (a2) is preferably thestructural unit (a2-1). The structural unit (a3) is preferably one ofthe structural unit (a3-1), the structural unit (a3-2) and thestructural unit (a3-4).

Resin (A) comprises preferably the structural unit (a1) derived from astructural unit having an adamantyl group, preferably structural unit(a1-1). The content of the structural unit having an adamantyl group ispreferably 15% by mole or more of the total amount of the structuralunit (a1). The more is the structural unit having an adamantyl group,the more improved is the resistance of the photoresist film to dryetching.

Resin (A) can be produced according to known polymerization methods suchas radical polymerization.

The resin has usually 2,000 or more of the weight-average molecularweight, preferably 2,500 or more of the weight-average molecular weight,more preferably 3,000 or more of the weight-average molecular weight.The resin has usually 50,000 or less of the weight-average molecularweight, preferably more 30,000 or less of the weight-average molecularweight, and preferably more 15,000 or less of the weight-averagemolecular weight.

The weight-average molecular weight can be measured with gel permeationchromatography.

<Fluororesin>

For the composition of the disclosure, the resin having a fluorine atom,which is sometimes referred to as “fluororesin”, comprises for example astructural unit having a fluorine atom.

Hereinafter, the structural unit having no acid-labile group but havinga fluorine atom is referred to as “structural unit (a4)”.

Examples of the structural unit (a4) include the following one.

Examples of the structural unit (a4) include one represented by formula(a4-0):

wherein R⁵ represents a hydrogen atom or a methyl group;L⁴ represents a single bond or a C1-C4 aliphatic saturated hydrocarbongroup;L³ represents a C1-C8 perfluoroalkanediyl group; andR⁶ represents a hydrogen atom or a fluorine atom.

Examples of the perfluoroalkanediyl group for L³ include adifluoromethylene group, a perfluoroethylene group, a (perfluoroethyl)fluoromethylene group, a perfluoropropane-1,3-diyl group, aperfluoropropane-1,2-diyl group, a perfluoropropane-2,2-diyl group, aperfluorobutane-1,4-diyl group, a perfluorobutane-2,2-diyl group, aperfluorobutane-1,2-diyl group, a perfluoropentane-1,5-diyl group, aperfluoropentane-2,2-diyl group, a perfluorohexane-1,6-diyl group, aperfluorohexane-2,2-diyl group, a perfluorohexane-3,4-diyl group, aperfluoroheptane-1,7-diyl group, a perfluoroheptane-2,2-diyl group, aperfluoroheptane-3,4-diyl group, a perfluoroheptane-4,4-diyl group, aperfluorooctane-1,8-diyl group, a perfluorooctane-2,2-diyl group, aperfluorooctane-3,3-diyl group and a perfluorooctane-4,4-diyl group.

L³ is preferably a C1-C6 perfluoroalkanediyl group, more preferably aC1-C3 perfluoroalkanediyl group.

Examples of the aliphatic saturated hydrocarbon group for L⁴ include aC1-C4 alkylene group such as a methylene group, an ethylene group, apropylene group and a butylene group.

L⁴ is preferably single bond, a methylene group or an ethylene group,more preferably single bond or a methylene group.

Examples of the structural unit represented by formula (a4-0) includethe following ones and those in which a methyl group has been replacedby a hydrogen atom in each of the following formulae.

Examples of the structural unit (a4) include one represented by formula(a4-1):

wherein R^(a41) represents a hydrogen atom or a methyl group;A^(a41) represents a C1-C6 divalent alkanediyl group which may have asubstituent or a moiety represented by formula (a-g1):

in which s represents an integer of 0 to 1,A^(a42) and A^(a44) respectively represent a C1-C5 aliphatic hydrocarbongroup which may have a substituent,A^(a43) represents a single bond or a C1-C5 aliphatic hydrocarbon groupwhich may have a substituent,X^(a41) and X^(a42) respectively represent —O—, —CO—, —CO—O—, or —O—CO—,provided that the sum of carbon atoms of A^(a42), A^(a43), A^(a44),X^(a41) and X^(a42) is 6 or less and A^(a44) is bonded to —O—CO-A^(a42);R^(a42) represents a C1-C20 monovalent hydrocarbon group which may havea substituent, provided that each or both of A^(a41) and R^(a42) have afluorine atom.

For formula (a4-1), the aliphatic hydrocarbon group is preferably adivalent saturated hydrocarbon group while it may have a carbon-carbondouble bond.

Examples of the aliphatic hydrocarbon group include alkanediyl groupswhich may be a linear or branched one, divalent alicyclic hydrocarbongroups, and combination of them.

Examples of the monovalent hydrocarbon group for R^(a42) includemonovalent chain or cyclic aliphatic hydrocarbon groups, an aromatichydrocarbon group and combination of them.

Examples of monovalent chain aliphatic hydrocarbon group include amethyl group, an ethyl group, a propyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group, an octyl group, a decyl group, adodecyl group, a hexadecyl group, a pentadecyl group, a hexyldecylgroup, heptadecyl group and an octadecyl group. Examples of monovalentcyclic aliphatic hydrocarbons include cycloalkyl groups such as acyclopentyl group, a cyclohexyl group, a cycloheptyl group and acyclooctyl group; and monovalent polycyclic hydrocarbon groups such as adecahydronaphthyl group, an adamantyl group, a norbornyl group, and thefollowing groups where * represents a binding position.

Examples of monovalent aromatic hydrocarbon groups include a phenylgroup, a naphthyl group, an anthryl group, a biphenylyl group, aphenanthryl group and a fluorenyl group.

The monovalent hydrocarbon group for R^(a42) is preferably monovalentchain and cyclic aliphatic hydrocarbon groups and combination of them,which may have a carbon-carbon double bond, and more preferably amonovalent chain aliphatic hydrocarbon group and cyclic hydrocarbongroup and combination of them.

The preferred monovalent chain aliphatic hydrocarbon groups are C1-C8alkyl groups such as a methyl group, an ethyl group, a propyl group, abutyl group, a pentyl group, a hexyl group, a 2-ethyhexyl group, anoctyl group. The preferred cyclic aliphatic hydrocarbon groups areC3-C10 cycloalkyl group such as a cyclopropy; group, a cyclobutyl group,a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and acyclooctyl group or a cyclodecyl group, and polycyclic cyclichydrocarbon groups such as decahydronaphthyl group, an adamantyl group,a 2-alkyladamantane-2-yl group, a 1-(adamantane-1-yl)alkane-1-yl group,a norbornyl group, a methylnorbornyl group, and an isonorbornyl group.

R^(a42) is preferably a chain and cyclic aliphatic hydrocarbon grouphydrocarbon group which has a substituent, more preferably a aliphatichydrocarbon group which has a halogen atom and/or a group represented byformula (a-g3).

—X^(a43)-A^(a45)  (a-g3)

in which X^(a43) represents an oxygen atom, a carbonyl group, acarbonyloxy group or an oxycarbonyl group,A^(a45) represents a C3-C17 monovalent saturated hydrocarbon group whichmay have a fluorine atom.

When R^(a42) is a monovalent saturated hydrocarbon group which has agroup represented by formula (a-g3), R^(a42) has preferably 15 or lesscarbon atoms, more preferably 12 or less carbon atoms in total includingthe carbon atoms of formula (a-g3). If R^(a42) has a group representedby formula (a-g3), the number of the group is preferably 1.

The monovalent saturated hydrocarbon group which has a group representedby formula (a-g3) is preferably a group represented by formula (a-g2):

-A^(a46)-X^(a44)-A^(a47)  (a-g2)

in which A^(a46) represents a C3-C17 divalent saturated hydrocarbongroup which may have a fluorine atom, X^(a44) represents a carbonyloxygroup or an oxycarbonyl group, and A^(a47) represents a C3-C17 divalentsaturated hydrocarbon group which may have a fluorine atom, providedthat A^(a46), A^(a47) and X^(a44) have 18 or less of carbon atoms intotal and one or both of A^(a46) and A^(a47) have a fluorine atom.

When R^(a42) is an aliphatic hydrocarbon group which has a halogen atom,it is preferably a monovalent fluorine-containing saturated hydrocarbongroup, more preferably a perfluoroalkyl group or a perfluorocycloalkylgroup, still more preferably a C1-C6 perfluoroalkyl group, and furthermore preferably a C1-C3 perfluoroalkyl group.

Examples of perfluoroalkyl group include a perfluoromethyl group, aperfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, aperfluoropentyl group, a perfluorohexyl group, a perfluoroheptyl group,and a perfluorooctyl group. Examples of the perfluorocycloalkyl groupinclude perfluorocyclohexyl group.

The divalent saturated hydrocarbon group represented by A^(a46) haspreferably 1 to 6, more preferably 1 to 3 carbon atoms.

The monovalent saturated hydrocarbon group represented by A^(a47) haspreferably 4 to 15, more preferably 5 to 12 carbon atoms. A^(a47) ismore preferably a cyclohexyl group or an adamantyl group. Examples ofthe moiety represented by -A^(a46)-A^(a44)-A^(a47) include the followingones.

In each formula, * represents a binding position to a carbonyl group.

Examples of A^(a41) typically include a C1-C6 alkanediyl group which maybe a linear chain or branched chain. Specific examples of them includelinear chain alkanediyl groups such as a methylene group, an ethylenegroup, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, or a hexane-1,6-diyl group; and branched chainalkanediyl groups such as a propane-1,3-diyl group, a butane-1,3-diylgroup, a 1-methylbutane-1,2-diyl group, or a 2-methylbutane-1,4-diylgroup. Examples of the substituents which such alkanediyl group may haveinclude a hydroxy group or a C1-C6 alkoxy group.

A^(a41) is preferably a C1-C4 alkanediyl group, more preferably a C2-C4alkanediyl group, and still more preferably an ethylene group.

Examples of the alkanediyl group represented by A^(a42), A^(a43) andA^(a44) include a methylene group, an ethylene group, a propane-1,3-diylgroup, a butane-1,4-diyl group, a 2-methylpropane-1,3-diyl group, or a2-methylbutane-1,4-diyl group. Examples of the substituents which suchalkanediyl group may have include a hydroxy group or a C1-C6 alkoxygroup.

X^(a42) represents —O—, —CO—, *—CO—O—**, or *—O—CO—**. Here, * and **represent binding sites, and ** represents a binding site to A^(a44).

Examples of the moiety represented by formula (a-g1) where X^(a42) is anoxygen atom, a carbonyl group, a carbonyloxy group or an oxycarbonylgroup include the following ones:

in which * and ** represent binding sites, and ** represents a bindingsite to —O—CO—R^(a42).

The structural unit represented by formula (a4-1) is preferably onerepresented by formula (a4-2) or (a4-3).

In formula, R^(f1) represents a hydrogen atom or a methyl group.

A^(f1) represents a C1-C6 alkanediyl group.

R^(f2) represents preferably C1-C10, monovalent hydrocarbon group havinga fluorine atom.

The alkanediyl groups represented by A^(f1) may be a linear chain orbranched chain. Specific examples of them include linear chainalkanediyl groups such as a methylene group, an ethylene group, apropane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, or a hexane-1,6-diyl group; and branched chain alkanediyl groupssuch as a propane-1,3-diyl group, a butane-1,3-diyl group, a1-methylbutane-1,2-diyl group, or a 2-methylbutane-1,4-diyl group.Examples of the substituents which such alkanediyl group may haveinclude a hydroxy group or a C1-C6 alkoxy group.

The monovalent hydrocarbon group represented by R^(f2) includesaliphatic hydrocarbon groups and aromatic hydrocarbon groups. Thealiphatic hydrocarbon groups may be a chain or cyclic aliphatichydrocarbon group, or a combined group of them.

The aliphatic hydrocarbon groups are preferably an alkyl group or analicyclic hydrocarbon group.

Examples of the alkyl group include a methyl group, an ethyl group,n-propyl group, isopropyl group, n-butyl group, sec-butyl group, atert-butyl group, a pentyl group, a hexyl group and 2-ethylhexyl group.

The alicyclic hydrocarbon groups may be monocyclic or polycyclic groups.Examples of the monocyclic hydrocarbon groups include a cyclopropylgroup, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, amethylcyclohexyl group, a dimethylcyclohexyl group, a cycloheptyl group,a cyclooctyl group, a cycloheptyl group and a cyclodecyl group.

Examples of the polycyclic hydrocarbon groups include adecahydronaphthyl group, an adamantyl group, a norbornyl group, and anisobornyl group.

Examples of the combined group of the above-mentioned hydrocarbon groupinclude a 2-alkyladamantane-2-yl group, a 1-(adamantane-1-yl)alkane-1-ylgroup, and a methylnorbornyl group.

Examples of monovalent hydrocarbon groups having a fluorine atom forR^(f2) include monovalent fluoroalkyl groups and monovalent fluorineatom-containing alicyclic hydrocarbon groups.

Specific examples of monovalent fluoroalkyl groups include afluoromethyl group, a trifluoromethyl group, 1,1-difluoroethyl group,2,2-difluoroethyl group, 2,2,2-trifluoroethyl group, perfluoroethylgroup, 1,1,2,2-tetrafluoropropyl group, 1,1,2,2,3,3-hexafluoropropylgroup, perfluoroethylmethyl group,1-(trifluoromethyl)-1,2,2,2-tetrafluoroethyl group, perfluoropropylgroup, 1,1,2,2-tetrafluorobutyl group, 1,1,2,2,3,3-hexafluorobutylgroup, 1,1,2,2,3,3,4,4-octafluorobutyl group, perfluorobutyl group,1,1-bis(trifluoro)methyl-2,2,2-trifluoroethyl group,2-(perfluoropropyl)ethyl group, 1,1,2,2,3,3,4,4-octafluoropentyl group,perfluoropentyl group, 1,1,2,2,3,3,4,4,5,5-decafluoropentyl group,1,1-bis(trifluoromethyl)-2,2,3,3,3-pentafluoropropyl group,2-(perfluorobutyl)ethyl group, 1,1,2,2,3,3,4,4,5,5-decafluorohexylgroup, 1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyl group, aperfluoropentylmethyl group and a perfluorohexyl group.

Specific examples of monovalent fluorine-containing alicyclichydrocarbon groups include fluorocycloalkyl groups such as aperfluorocyclohexyl group and a perfluoroadamantyl group.

In formula (a4-2), A^(f1) is preferably a C2-C4 alkylene group, and morepreferably an ethylene group. R^(f2) is preferably a C1-C6 fluoroalkylgroup.

In formula, R^(f11) represents a hydrogen atom or a methyl group.

A^(f11) represents a C1-C6 alkanediyl group.

A^(f13) represents a C1-C18 aliphatic hydrocarbon group which may have afluorine atom.

X^(f12) represents a carbonyloxy group or an oxycarbonyl group.

A^(f14) represents a C1-C17 aliphatic hydrocarbon group which may have afluorine atom, provided that one or both of A^(f13) and A^(f14)represents a fluorine-containing saturated hydrocarbon group.

Examples of the alkanediyl group represented by A^(f11) include those asreferred to for A^(f1).

As to A^(f13), the aliphatic hydrocarbon group includes chain aliphatichydrocarbon groups, cyclic aliphatic hydrocarbon groups and combinedgroups of these groups.

As to A^(f13), the aliphatic hydrocarbon group which may have a fluorineatom is preferably an aliphatic chain hydrocarbon group which may have afluorine atom, more preferably a perfluoroalkanediyl group. Examples ofthe aliphatic hydrocarbon group which may have a fluorine atom includean alkanediyl group such as a methyl group, an ethylene group, apropanediyl group, a butanediyl group and pentanediyl group; and aperfluoroalkanediyl group such as a difluoromethylene group, aperfluoroethylene group, a perfluoropropanediyl group, aperfluorobutanediyl group and perfluoropentanediyl group. The cyclicaliphatic hydrocarbon group which may have a fluorine atom may be adivalent monocyclic or polycyclic group.

Examples of the divalent monocyclic hydrocarbon group which may have afluorine atom include a cyclohexanediyl group and aperfluorocyclohexanediyl group.

Examples of the divalent polycyclic hydrocarbon group which may have afluorine atom include an adamantanediyl group, norbornanediyl group, anda perfluoroadamantanediyl group.

In the group represented by A^(f14), the aliphatic hydrocarbon groupincludes chain aliphatic hydrocarbon groups, cyclic aliphatichydrocarbon groups and the combination thereof.

As to A^(f14), the aliphatic hydrocarbon group which may have a fluorineatom is preferably an aliphatic saturated hydrocarbon group which mayhave a fluorine atom, more preferably a perfluoroalkanediyl group.

Examples of the aliphatic hydrocarbon group which may have a fluorineatom include a trifluoromethyl group, a fluoromethyl group, a methylgroup, a perfluoroethyl group, a 1,1,1-trifluoroethyl group, a1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group,a 1,1,1,2,2-pentafluoropropyl group, propyl group, a perfluorobutylgroup, 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, aperfluoropentyl group, 1,1,1,2,2,3,3,4,4-nonafluoropentyl group, apentyl group, a hexyl group, a perfluorohexyl group, a heptyl group, aperfluoroheptyl group, an octyl group and a perfluorooctyl group.

The monovalent cyclic hydrocarbon group which may have a fluorine atommay be monocyclic or polycyclic monovalent group.

Examples of the monocyclic aliphatic hydrocarbon group which may have afluorine atom include a cyclopropyl group, a cyclopentyl group, acyclohexyl group, and a perfluorocyclohexyl group.

Examples of the polycyclic aliphatic hydrocarbon group which may have afluorine atom include an adamantyl group, a norbornyl group, and aperfluoroadamantyl group.

Examples of the combined groups of the above-mentioned aliphatichydrocarbon groups include a cyclopropylmethyl group, a cyclobutylmethylgroup, an adamantylmethyl group, a norbornylmethyl group and aperfluoroadamantylmethyl group.

In formula (a4-3), A^(f11) is preferably an ethylene group.

The aliphatic hydrocarbon group represented by A^(f13) has preferably 6or less, more preferably 2 to 3, of carbon atoms.

The aliphatic hydrocarbon group represented by A^(f14) has preferably 3to 12, more preferably 3 to 10, of carbon atoms.

A^(f14) has preferably a C3-C12 alicyclic hydrocarbon group, morepreferably a cyclopropylmethyl group, a cyclopentyl group, a cyclohexylgroup, a norbornyl group or an adamantyl group.

Examples of the structural unit of formula (a4-2) include preferablythose represented by formulae (a4-1-1) to (a4-1-22).

Examples of the structural unit represented by formula (a4-3) includepreferably those represented by formulae (a4-1′-1) to (a4-1′-22).

Another example of the structural unit (a4) includes those representedby formula (a4-4).

In formula (a4-4), R^(f21) represents a hydrogen atom or a methyl group;

A^(f21) represents —(CH₂)_(j1)—, —(CH₂)_(j2)—O—(CH₂)_(j3)— or(CH₂)_(j4)—CO—O—(CH₂)_(j5)— where j1, j2, j3, j4 or j5 eachindependently represent an integer of 1 to 6; andR^(f22) represents a C1-C10 monovalent hydrocarbon group having afluorine atom.

For R^(f22), examples of monovalent hydrocarbon group having a fluorineatom include those as referred to for R^(f2).

R^(f22) is preferably a C1-C10 monovalent alkyl group having a fluorineatom or a C3-C10 monovalent alicyclic hydrocarbon group having afluorine atom, more preferably a C1-C10 monovalent alkyl group having afluorine atom, and still more preferably a C1-C6 monovalent alkyl grouphaving a fluorine atom.

In formula (a4-4), A^(f21) is preferably —(CH₂)_(j1)—, more preferably amethylene or ethylene group, and still more preferably a methylenegroup.

Examples of the structural unit represented by formula (a4-4) includepreferably the following ones.

In the fluororesin, its content of the structural unit (a4) ispreferably 40% or more by mole, more preferably 45% or more by mole,still more preferably 50% or more by mole, and further more preferably80% or more, by mole based on 100% by mole of all the structural unitsof the resin.

The fluororesin may further comprise another structural unit such as thestructural unit (a1), the structural unit (a2), the structural unit(a3), the structural unit (a5) and a structural unit known in the art.

The fluororesin usually has 8000 or more of the weight-average molecularweight, preferably 10000 or more of the weight-average molecular weight.The resin usually has 80,000 or less of the weight-average molecularweight, preferably has 60,000 or less of the weight-average molecularweight.

The weight-average molecular weight can be measured with known methodssuch as liquid chromatography or gas chromatography.

The content of the fluororesin is preferably 1 to 60 weight parts, morepreferably 1 to 50 weight parts, and still more preferably 1 to 40weight parts, and further still more preferably 2 to 30 weight parts,relative to 100 parts of Resin (A). Its content may be in the range of 7to 30 weight parts relative to 100 parts of Resin (A).

The photoresist composition of the disclosure may further compriseanother resin than Resin (A) and fluororesin, if necessary.

Examples of the another resin include what comprises a structural unithaving neither an acid-labile group nor a fluorine atom. Examples of thestructural unit for the another resin include one which has no acidlabile group such as the structural units (a2), (a3) and (a5).

The total content of the resins in the photoresist composition of thedisclosure is usually 80% by mass or more based on sum of solidcomponent, and usually 99% by mass or less.

In this specification, “solid component” means components other thansolvent in the photoresist composition.

The photoresist composition of the disclosure may comprise a solvent.

The amount of the solvent is usually 90% by weight or more, preferably92% by weight or more preferably 94% by weight or more based on totalamount of the photoresist composition of the disclosure.

The amount of the solvent is usually 99.9% by weight or less andpreferably 99% by weight or less based on total amount of thephotoresist composition of the disclosure. The content can be measuredwith known methods such as liquid chromatography or gas chromatography.

Examples of the solvent include a glycol ether ester such as ethylcellosolve acetate, methyl cellosolve acetate and propylene glycolmonomethyl ether acetate; a glycol ether such as propylene glycolmonomethyl ether; an ester such as ethyl lactate, butyl acetate, amylacetate and ethyl pyruvate; a ketone such as acetone, methyl isobutylketone, 2-heptanone and cyclohexanone; and a cyclic ester such asγ-butyrolactone. The photoresist composition may comprise two or moresolvents.

The photoresist compositions of the disclosure may further comprise aquencher such as a basic compound. The “quencher” has the property thatit can trap an acid, especially an acid generated from the acidgenerator by applying radiation thereto.

Examples of the quencher include a basic compound, such as a basicnitrogen-containing organic compound, and a salt which generates an acidhaving acidity weaker than an acid generated from the compoundrepresented by formula (I).

Examples of the basic nitrogen-containing organic compound include anamine compound such as an aliphatic amine, an aromatic amine and anammonium salt. Examples of the aliphatic amine include a primary amine,a secondary amine and a tertiary amine. Examples of the aromatic amineinclude an aromatic amine.

Examples of the quencher include 1-naphthylamine, 2-naphthylamine,aniline, diisopropylaniline, 2-, 3- or 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine,heptylamine, octylamine, nonylamine, decylamine, dibutylamine,pentylamine, dioctylamine, triethylamine, trimethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine,methyldibutylamine, methyldipentylamine, methyldihexylamine,methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine,methyldinonylamine, methyldidecylamine, ethyldibutylamine,ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine,ethyldioctylamine, ethyldinonylamine, ethyldidecylamine,dicyclohexylmethylamine, 2 tris[2-(2-methoxyethoxyl)ethyl]amine,triisopropanolamine, ethylenediamine, tetramethylenediamine,hexamethylenediamine, 4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4-diamino-3,3′-diethyldiphenyl methane, piperazine, morpholine,piperidine, hindered amine compound having a piperidine structure,2,2′-methylenebisaniline, imidazole, 4-methylimidazole, pyridine,4-methylpyridine, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane, di(2-pyridyl)ketone, 4,4′-dipyridylsulfide, 4,4′-dipyridyl disulfide, 2,2′-dipyridylamine,2,2′-dipicolylamine and bipyridine.

Examples of the quaternary ammonium hydroxide includetetramethylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethylammonium hydroxide,(3-trifluoromethylphenyl)trimethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”).

Herein, the acidity in the salts is shown by the acid dissociationconstant (pKa).

The acid dissociation constant of acid generated from the salt for aquencher is usually a salt of −3<pKa.

The salt for a quencher is preferably a salt of −1<pKa<7, and morepreferably a salt of 0<pKa<5.

Specific examples of the salt for a quencher include the following ones,the salt of formula (D), and salts recited in US2012/328986A1,US2011/171576A1, US2011/201823A1, JP2011-39502A1, and US2011/200935A1.

In formula (D), R^(D1) and R^(D2) respectively represent a C1-C12monovalent hydrocarbon group, a C1-C6 alkoxy group, a C2-C7 acyl group,a C2-C7 acyloxy group, a C2-C7 alkoxycarbonyl group, a nitro group or ahalogen atom.

The symbols m′ and n′ each independently represent an integer of 0 to 4,preferably an integer of 0 to 2, and more preferably 0. The hydrocarbongroup represented by R^(D1) and R^(D2) includes a C1-C12 alkyl group, aC3-C12 monovalent alicyclic hydrocarbon group, a C6-C12 monovalentaromatic hydrocarbon group, and any combination of them.

Examples of the monovalent hydrocarbon group include alkyl groups suchas a methyl group, an ethyl group, n-propyl group, an isopropyl group,n-butyl group, sec-butyl group, tert-butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group. Examples ofthe alicyclic hydrocarbon group, which may be a monocyclic or polycyclicone, include cycloalkyl groups such as a cyclopropyl group, a cyclobutylgroup, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, acyclooctyl group, a cycloheptyl group, a cyclodecyl group, and norbonylgroup and adamantyl group. Examples of the aromatic hydrocarbon groupinclude an aryl group such as a phenyl group, a 1-naphthyl group, a2-naphthyl group, a 2-methylphenyl group, a 3-methylphenyl group,4-methylphenyl group, a 4-ethylphenyl group, a 4-propylphenyl group, a4-isopropylphenyl group, a 4-butylphenyl group, a 4-t-butylphenyl group,a 4-hexylphenyl group, a 4-cyclohexylphenyl group, an anthryl group, ap-adamantylphenyl group, a tolyl group, a xylyl group, a cumenyl group,a mesityl group, a biphenyl group, a phenanthryl group, a2,6-diethylphenyl group and a 2-methyl-6-ethylphenyl group. Examples ofthe combination include alkyl-cycloalkyl groups, cycloalkyl-alkylgroups, aralkyl groups such as a benzyl group, a 1-phenylethyl group, a2-phenylethyl group, a 1-phenyl-1-propyl group, a 1-phenyl-2-propylgroup, a 2-phenyl-2-propyl group, a 3-phenyl-1-propyl group, a4-phenyl-1-butyl, a 5-phenyl-1-pentyl group and 6-phenyl-1-hexyl group.

Examples of alkoxy groups include a methoxy group and an ethoxy group.

Examples of acyl groups include an acetyl group, a propanoyl group, abenzoyl group and a cyclohexanecarbonyl group.

Examples of acyloxy group include groups where an oxy group [—O—] isattached to any one of the acyl groups as mentioned above.

Examples of alkoxycarbonyl group include groups where a carbonyl group[—CO—] is attached to any one of the alkoxy groups as mentioned above.

Examples of halogen atoms include fluorine atoms, a chlorine atom, and abromine atom.

Examples of the compounds of formula (D) include the following ones.

The compound represented by formula (D) can be produced according to themethod recited in Tetrahedron Vol. 45, No. 19, p6281-6296. The compoundis available on the market.

The content of quencher is preferably 0.01 to 5% by mass, morepreferably 0.01 to 4% by mass, still more preferably 0.01 to 3% by mass,and further more preferably 0.01 to 1% by mass, based on sum of solidcomponent.

The photoresist compositions of the disclosure may comprise, ifnecessary, a small amount of various additives such as a sensitizer, adissolution inhibitor, other polymers, a surfactant, a stabilizer and adye as long as the effect of the present invention is not prevented.

The photoresist compositions of the disclosure can usually be preparedby mixing, in a solvent, Resin (A), the fluororesin, and the saltrepresented by formula (I), and if necessary a quencher, and/oradditives at a suitable ratio for the composition, optionally followedby filtrating the mixture with a filter having 0.003 μm to 0.2 μm of apore size.

The order of mixing these components is not limited to any specificorder. The temperature at mixing the components is usually 10 to 40° C.,which can be selected in view of the resin or the like.

The mixing time is usually 0.5 to 24 hours, which can be selected inview of the temperature. The means for mixing the components is notlimited to specific one. The components can be mixed by being stirred.

The amounts of the components in the photoresist compositions can beadjusted by selecting the amount to be used for production of them.

The photoresist compositions of the disclosure are useful for achemically amplified photoresist composition.

The photoresist compositions of the disclosure are useful for achemically amplified photoresist composition.

A photoresist pattern can be produced by the following steps (1) to (5):

(1) a step of applying the photoresist composition of the disclosure ona substrate,

(2) a step of forming a composition film by conducting drying,

(3) a step of exposing the composition film to radiation,

(4) a step of baking the exposed composition film, and

(5) a step of developing the baked composition film with an alkalinedeveloper.

The applying of the photoresist composition on a substrate is usuallyconducted using a conventional apparatus such as spin coater. Thephotoresist composition is preferably filtrated with filter having apore size of 0.01 to 0.2 μm before applying. Examples of the substrateinclude a silicon wafer or a quartz wafer on which a sensor, a circuit,a transistor or the like is formed.

The formation of the composition film is usually conducted using aheating apparatus such as hot plate or a decompressor, and the heatingtemperature is usually 50 to 200° C. When the pressure is reduced duringheating, the operation pressure is usually 1 to 1.0*10⁵ Pa. The heatingtime is usually 10 to 180 seconds.

The composition film obtained is exposed to radiation using an exposuresystem. The exposure is usually conducted through a mask having apattern corresponding to the desired photoresist pattern. Examples ofthe exposure source include a light source radiating laser light in aUV-region such as a KrF excimer laser (wavelength: 248 nm), an ArFexcimer laser (wavelength: 193 nm) and a F₂ laser (wavelength: 157 nm),and a light source radiating harmonic laser light in a far UV region ora vacuum UV region by wavelength conversion of laser light from a solidlaser light source (such as YAG or semiconductor laser).

The temperature of baking of the exposed composition film is usually 50to 200° C., and preferably 70 to 150° C.

The development of the baked composition film is usually carried outusing a development apparatus. The development method includes dippingmethods, paddle methods, spray methods and dynamic dispense method. Thedeveloping temperature is preferably 5 to 60° C., and the developingtime is preferably 5 to 300 seconds.

The positive and negative type photoresist patterns can be obtained bythe development depending on a developer to be used therefor.

When a positive type photoresist pattern is prepared from thephotoresist composition of the disclosure, the development can beconducted with an alkaline developer. The alkaline developer to be usedmay be any one of various alkaline aqueous solution used in the art.Generally, an aqueous solution of tetramethylammonium hydroxide or(2-hydroxyethyl)trimethylammonium hydroxide (commonly known as“choline”) is often used. The alkaline developer may comprise asurfactant.

After development, the photoresist film having photoresist pattern ispreferably washed with ultrapure water, and the remained water on thephotoresist film and the substrate is preferably removed therefrom.

When a negative type photoresist pattern is prepared from thephotoresist composition of the disclosure, the development can beconducted with a developer containing an organic solvent, such developeris sometimes referred to as “organic developer”. Examples of an organicsolvent for organic developer include ketone solvents such as2-hexanone, 2-heptanone; glycolether ester solvents such aspropyleneglycolmonomethylether acetate; ester solvents such as butylacetate; glycolether solvents such as propyleneglycolmonomethylether;amide solvents such as N,N-dimethylacetamide; and aromatic hydrocarbonsolvents such as anisole.

The content of organic solvent is preferably from 90% to 100% by weight,more preferably from 95% to 100% by weight, in an organic developer.Preferred is that the organic developer essentially consists of anorganic solvent.

Among them, the organic developer is preferably a developer comprisingbutyl acetate and/or 2-heptanone.

The total content of butyl acetate and 2-heptanone is preferably from50% to 100% by weight, more preferably from 90% to 100% by weight.Preferred is that the organic developer essentially consists of butylacetate and/or 2-heptanone.

The organic developer may comprise a surfactant or a very small amountof water.

Development with an organic developer can be stopped by replacing thedeveloper by other solvent than it such as alcohol.

The photoresist composition of the disclosure is suitable for KrFexcimer laser lithography, ArF excimer laser lithography, EUV (extremeultraviolet) lithography, EUV immersion lithography and EB (electronbeam) lithography.

EXAMPLES

The present invention will be described more specifically by Examples,which are not construed to limit the scope of the disclosure.

The “%” and “part(s)” used to represent the content of any component andthe amount of any material used in the following examples andcomparative examples are on a mass basis unless otherwise specificallynoted.

The weight-average molecular weight of any material used in thefollowing examples was determined with gel permeation chromatographyunder the following condition.

Equipment: HLC-8120 GPC type, manufactured by TOSOH CORPORATION

Column: Three of TSKgel Multipore HXL-M with guard column, manufacturedby TOSOH CORPORATION Solvent: tetrahydrofuran

Flow rate: 1.0 mL/min.

Detector: RI Detector

Column temperature: 40° C.

Injection volume: 100 μL

Standard reference material: Standard polystyrene (manufactured by TOSOHCORPORATION)

Structures of compounds were determined by mass spectrometry (LiquidChromatography: 1100 Type, manufactured by AGILENT TECHNOLOGIES LTD.,Mass Spectrometry: LC/MSD Type, manufactured by AGILENT TECHNOLOGIESLTD.).

Here, the values at the peaks of the spectrum are referred to as “MASS.”

Synthesis Example 1

To a reactor, 3 parts of the compound represented by formula (I-19-a), 3parts of chloroform were added and then they were stirred at 23° C. for30 minutes.

Then to the obtained mixture, 7.35 parts of AgClO₄ and 12.5 parts of thecompound represented by formula (I-19-b) were added and stirred at 23°C. for 4 days. The obtained reaction mixture was concentrated, and thento the collected concentrated residues 9 parts of acetonitrile and 110parts of tert-butylmethylether were added and stirred for 30 minutes.Then the mixture was filtrated to collect 7 parts of the saltrepresented by formula (I-19-c).

To a reactor, 8.00 parts of compounds represented by formula (I-19-d),40 parts of chloroform and 12 parts of ion exchanged water were addedand stirred at 23° C. for 30 minutes. To the obtained mixture, 18.32parts of 5% oxalic acid water solution and 3.10 parts of compoundrepresented by formula (I-19-c) were added and further stirred at 23° C.for one hour.

From the reaction mixture having two layers, the chloroform layer wasseparated and taken out, and then 12 parts of ion exchanged water wasadded to the chloroform layer, followed by washing with water. Thewashing step was conducted five times.

The washed layer was concentrated, and then to the concentrated one,2.39 parts of acetonitrile and 35.85 parts of tert-butylmethylether wereadded, and stirred at 23° C. for 30 minutes and removed supernatanttherefrom, followed by being concentrated.

As a result, 3.58 parts of the salt represented by formula (I-19) wasobtained.

MASS (ESI (+) Spectrum): M⁺ 433.1

MASS (ESI (−) Spectrum): M⁺ 339.1

Synthesis Example 2

To a reactor, 7.71 part of the compound represented by formula (I-20-d)and 40 parts of chloroform were added, and stirred at 23° C. for 30minutes.

To the obtained mixture, 18.32 parts of 5% oxalic acid water solutionand 3.10 parts of compound represented by formula (I-19-c) were addedand further stirred at 23° C. for one hour.

From the reaction mixture having two layers, the chloroform layer wasseparated and taken out, and then 12 parts of ion exchanged water wasadded to the chloroform layer, followed by washing with water. Thewashing step was conducted five times.

The washed layer was concentrated, and then to the concentrated one, 40parts of tert-butylmethylether were added, and stirred at 23° C. for 30minutes and removed supernatant therefrom, followed by beingconcentrated. As a result, 3.38 parts of the salt represented by formula(I-20) was obtained.

MASS (ESI (+) Spectrum): M⁺ 433.1

MASS (ESI (−) Spectrum): M⁻ 323.1

Synthesis Example 3

To a reactor, 4.03 parts of the compound represented by formula (I-49-a)and 4 parts of chloroform were added and then they were stirred at 23°C. for 30 minutes.

Then to the obtained mixture, 7.35 parts of AgClO₄ and 12.5 parts of thecompound represented by formula (I-49-b) were added and stirred at 23°C. for 4 days.

The obtained reaction mixture was concentrated, and then to thecollected concentrated residues 10 parts of acetonitrile and 100 partsof tert-butylmethylether were added and stirred for 30 minutes.

Then the mixture was filtrated to collect 7.13 parts of the saltrepresented by formula (I-49-c).

To a reactor, 8 part of the compound represented by formula (I-49-d), 40parts of chloroform, and 12 parts of ion-exchanged water were added, andstirred at 23° C. for 30 minutes.

To the obtained mixture, 18.32 parts of 5% oxalic acid water solutionand 3.47 parts of compound represented by formula (I-49-c) were addedand further stirred at 23° C. for one hour.

From the reaction mixture having two layers, the chloroform layer wasseparated and taken out, and then 12 parts of ion exchanged water wasadded to the chloroform layer, followed by washing with water. Thewashing step was conducted five times.

The washed layer was concentrated, and then to the concentrated one, 2parts of acetonitrile and 40 parts of tert-butylmethylether were added,and stirred at 23° C. for 30 minutes and removed supernatant therefrom,followed by being concentrated. As a result, 2.98 parts of the saltrepresented by formula (I-49) was obtained.

MASS (ESI (+) Spectrum): M⁺ 497.2

MASS (ESI (−) Spectrum): M⁻ 339.1

Synthesis Example 4

To a reactor, 7.71 part of the compound represented by formula (I-50-d),40 parts of chloroform, and 12 parts of ion-exchanged water were added,and stirred at 23° C. for 30 minutes. To the obtained mixture, 18.32parts of 5% oxalic acid water solution and 3.47 parts of compoundrepresented by formula (I-49-c) were added and further stirred at 23° C.for one hour.

From the reaction mixture having two layers, the chloroform layer wasseparated and taken out, and then 12 parts of ion exchanged water wasadded to the chloroform layer, followed by washing with water. Thewashing step was conducted five times.

The washed layer was concentrated. Then to the concentrated one, 40parts of tert-butylmethylether was added and stirred at 23° C. for 30minutes and removed supernatant therefrom, followed by beingconcentrated. As a result, 2.78 parts of the salt represented by formula(I-50) was obtained.

MASS (ESI (+) Spectrum): M⁺ 497.2

MASS (ESI (−) Spectrum): M⁻ 323.0

Synthesis Example 5

To a reactor, 3.28 parts of the compound represented by formula (I-55-a)and 3 parts of chloroform were added and then they were stirred at 23°C. for 30 minutes.

Then to the obtained mixture, 7.35 parts of AgClO₄ and 12.5 parts of thecompound represented by formula (I-55-b) were added and stirred at 23°C. for 4 days.

The obtained reaction mixture was concentrated, and then to thecollected concentrated residues 50 parts of tert-butylmethylether wasadded and stirred for 30 minutes. Then the mixture was filtrated tocollect 4.28 parts of the salt represented by formula (I-55-c).

To a reactor, 8 parts of the compound represented by formula (I-55-d),40 parts of chloroform and 12 parts of ion-exchanged water were added,and stirred at 23° C. for 30 minutes.

To the obtained mixture, 18.32 parts of 5% oxalic acid water solutionand 3.2 parts of compound represented by formula (I-55-c) were added andfurther stirred at 23° C. for one hour.

From the reaction mixture having two layers, the chloroform layer wasseparated and taken out, and then 12 parts of ion exchanged water wasadded to the chloroform layer, followed by washing with water. Thewashing step was conducted five times.

The washed layer was concentrated, and then to the concentrated one, 50parts of tert-butylmethylether was added, and stirred at 23° C. for 30minutes, followed by being filtrated. As a result, 2.22 parts of thesalt represented by formula (I-55) was obtained.

MASS (ESI (+) Spectrum): M⁺ 451.0

MASS (ESI (−) Spectrum): M⁻ 339.1

Synthesis Example 6

To a reactor, 50.49 parts of the salt represented by formula (B1-5-a)and 252.44 parts of chloroform were added and they were stirred at 23°C. for 30 minutes. Then 16.27 parts of the salt represented by formula(B1-5-b) were dropped thereto and then stirred at 23° C. for an hour toobtain a solution containing the salt represented by formula (B1-5-c).

To the obtained solution, 48.8 parts of the salt represented by formula(B1-5-d) and 84.15 parts of ion-exchanged water were added then stirredat 23° C. for 12 hours to obtain a reaction solution with two separatedphases. Then chloroform layer was separated therefrom, and 84.15 partsof ion-exchanged water were added thereto for washing: This washing stepwas conducted 5 times.

To the washed chloroform layer, 3.88 parts of active carbon were addedand then they were stirred, followed by conducting filtration.

The collected filtrate was concentrated. To the obtained residue, 125.87parts of acetonitrile was added and stirred, followed by beingconcentrated.

To the obtained residue, 20.62 parts of acetonitrile and 309.30 parts oftert-butylmethylether were added and stirred at 23° C. for 30 minutes,followed by removing its supernatant therefrom. Then To the residue, 200parts of n-heptane were added and stirred at 23° C. for 30 minutes,followed by being filtrated to obtain 61.54 parts of the saltrepresented by formula (B1-5).

MASS (ESI(+) Spectrum): M⁺ 375.2

MASS (ESI(−) Spectrum): M⁻ 339.1

Synthesis Example 7

In a reactor, 30.00 parts of the salt represented by formula (B1-21-b)which had been produced according to the method described in JP2008-209917A1, 35.50 parts of the salt represented by formula (B1-21-a),100 parts of chloroform and 50 parts of ion-exchanged water were fed andstirred at 23° C. for 15 hours. From the obtained reaction mixture whichhad two phases, a chloroform phase was collected with separation.

The chloroform phase was washed with 30 parts of ion-exchanged water forwashing: This washing was conducted five times.

The washed chloroform phase was concentrated. To the obtained residue,100 parts of tert-butylmethylether was added and then stirred at 23° C.for 30 minutes, followed by being filtrated to obtain 48.57 parts of thesalt represented by formula (B1-21-c).

Into a reactor, 20.00 parts of the salt represented by formula(B1-21-c), 2.84 parts of the compound represented by formula (B1-21-d)and 250 parts of monochlorobenzene were fed and then they were stirredat 23° C. for 30 minutes.

To the resultant mixture, 0.21 part of copper (II) dibenzoate was added.The resultant mixture was stirred at 100° C. for 1 hour. The mixture wasconcentrated, and then 200 parts of chloroform and 50 parts ofion-exchanged water were added to the obtained residue, followed bybeing stirred at 23° C. for 30 minutes. Then the organic phase wascollected by separation. The organic layer was washed with 50 parts ofion-exchanged water and then they were stirred at 23° C. for 30 minutes,followed by collecting an organic phase by separation: This washing wasconducted five times.

The washed organic layer was concentrated. To the residue, 53.51 partsof acetonitrile was added, and the resultant mixture was concentrated.To the residue, 113.05 parts of tert-butylmethylether was added and thenthey were stirred, followed by being filtrated to obtain 10.47 parts ofthe salt represented by formula (B1-21).

MASS (ESI(+) Spectrum): M⁺ 237.1

MASS (ESI(−) Spectrum): M⁻ 339.1

Synthesis Example 8

Into a reactor, 11.26 parts of the salt represented by formula(B1-22-a), 10.00 parts of the compound represented by formula (B1-22-b),50 parts of chloroform and 25 parts of ion-exchanged water were fed andthen they were stirred at 23° C. for 15 hours. From the obtainedreaction mixture which had two phases, a chloroform phase was collectedwith separation.

The chloroform phase was washed with 15 parts of ion-exchanged water forwashing: This washing was conducted five times.

The washed chloroform phase was concentrated. To the obtained residue,50 parts of tert-butylmethylether was added and then stirred at 23° C.for 30 minutes, followed by being filtrated to obtain 11.75 parts of thesalt represented by formula (B1-22-c).

Into a reactor, 11.71 parts of the salt represented by formula(B1-22-c), 1.70 parts of the compound represented by formula (B1-22-d)and 46.84 parts of monochlorobenzene were fed and then they were stirredat 23° C. for 30 minutes.

To the resultant mixture, 0.12 part of copper (II) dibenzoate wereadded. The resultant mixture was stirred at 100° C. for 30 minutes. Themixture was concentrated, and then 50 parts of chloroform and 12.50parts of ion-exchanged water were added to the obtained residue,followed by being stirred at 23° C. for 30 minutes. Then the organicphase was collected by separation. The organic layer was washed with12.50 parts of ion-exchanged water and then they were stirred at 23° C.for 30 minutes, followed by collecting an organic phase by separation:This washing was conducted eight times.

The washed organic layer was concentrated. To the residue, 50 parts oftert-butylmethylether was added, followed by being filtrated to obtain6.84 parts of the salt represented by formula (B1-22).

MASS (ESI(+) Spectrum): M⁺ 237.1

MASS (ESI(−) Spectrum): M⁻ 323.0

Compounds used as monomers in the following Synthesis Examples are shownas follow.

Here, each of the compounds is referred as to “monomer (X)” where “X” isthe symbol of the formula representing the monomer.

Synthesis Example 9

There were mixed monomers (a1-1-3), (a1-2-9), (a2-1-3) and (a3-4-2) in amolar ratio of 45/14/2.5/38.5 (monomer (a1-1-3)/monomer (a1-2-9)/monomer(a2-1-3)/monomer (a3-4-2)) as well as propyleneglycolmonomethyletheracetate in 1.5 times part based on total parts of all monomers toprepare a mixture. To the mixture, azobisisobutyronitrile as aninitiator in the ratio of 1 mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in the ratio of 3 mol% based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours. The reaction mixture was pouredinto a large amount of a mixture of methanol and water to causeprecipitation. The precipitate was collected by filtration.

Then the filtrates were dissolved in propyleneglycolmonomethyletheracetate and the resultant solution was poured into a large amount of amixture of methanol and water to cause precipitation, followed by beingfiltrated: This operation was conducted twice for purification.

As a result, a resin having a weight-average molecular weight of about7.6×10³ was obtained in yield of 68%. This resin is called as Resin A1.Resin A1 had the following structural units.

Synthesis Example 10

There were mixed monomers (a1-1-2), (a2-1-1) and (a3-1-1) in a molarratio of 50/25/25 [monomer (a1-1-2)/monomer (a2-1-1)/monomer (a3-1-1)]as well as propyleneglycolmonomethylether acetate in 1.5 times partbased on total parts of all monomers to prepare a mixture.

To the mixture, azobisisobutyronitrile as an initiator in the ratio of 1mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in the ratio of 3 mol% based on all monomer molar amount were added, and the obtained mixturewas heated at 75° C. for about 5 hours. The reaction mixture was pouredinto a large amount of a mixture of methanol and water to causeprecipitation. The precipitate was collected by filtration.

Then the filtrates were dissolved in propyleneglycolmonomethyletheracetate and the resultant solution was poured into a large amount of amixture of methanol and water to cause precipitation, followed by beingfiltrated: This operation was conducted twice for purification.

As a result, a resin having a weight-average molecular weight of about9.1×10³ was obtained in yield of 66%. This resin is called as resin A2.Resin A2 had the following structural units.

Synthesis Example 11

There were mixed monomer (a4-1-7) and 1,4-dioxane in 1.5 times partbased on total parts of all monomers to prepare a mixture. To themixture, azobisisobutyronitrile as an initiator in the ratio of 0.7 mol% based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in the ratio of 2.1mol % based on all monomer molar amount were added, and the obtainedmixture was heated at 75° C. for about 5 hours.

The reaction mixture was poured into a large amount of a mixture ofmethanol and water to cause precipitation. The precipitate was collectedby filtration.

Then the reaction mixture was poured into a large amount of a mixture ofmethanol and water to cause precipitation. The precipitate was collectedby filtration: This operation was conducted twice for purification.

As a result, a resin having a weight-average molecular weight of about1.8×10⁴ was obtained in yield of 77%. This resin is called as resin X1.Resin X1 had the following structural unit.

Synthesis Example 12

There were mixed monomers (a5-1-1) and (a4-0-1) in a molar ratio of75/25 [monomers (a5-1-1)/monomer (a4-0-1)] as well asmethylisobutylketone in 1.2 times part based on total parts of allmonomers to prepare a mixture.

To the mixture, azobis(2,4-dimethylvaleronitrile) as an initiator in theratio of 2 mol % based on all monomer molar amount was added, and theobtained mixture was heated at 70° C. for about 5 hours.

The reaction mixture was poured into a large amount of a mixture ofmethanol and water to cause precipitation.

As a result, a resin having a weight-average molecular weight of about1.7×10⁴ was obtained in yield of 87%. This resin is called as resin X2.Resin X2 had the following structural units.

Synthesis Example 13

There were mixed monomers (a5-1-1) and (a4-0-12) in a molar ratio of50/50 [monomers (a5-1-1)/monomer (a4-0-12)] as well asmethylisobutylketone in 1.2 times part based on total parts of allmonomers to prepare a mixture.

To the mixture, azobis(2,4-dimethylvaleronitrile) as an initiator in theratio of 3 mol % based on all monomer molar amount was added, and theobtained mixture was heated at 70° C. for about 5 hours.

The reaction mixture was poured into a large amount of a mixture ofmethanol and water to cause precipitation.

As a result, a resin having a weight-average molecular weight of about1.0×10⁴ was obtained in yield of 91%. This resin is called as resin X3.Resin X3 had the following structural units.

Synthesis Example 14

There were mixed monomer (a4-0-12) and 1,4-dioxane in 1.2 times partbased on total parts of all monomers to prepare a mixture. To themixture, azobis(2,4-dimethylvaleronitrile) as an initiator in the ratioof 3 mol % based on all monomer molar amount, and the obtained mixturewas heated at 70° C. for about 5 hours.

The reaction mixture was poured into a large amount of a mixture ofmethanol and water to cause precipitation. The precipitate was collectedby filtration.

Then the reaction mixture was poured into a large amount of a mixture ofmethanol and water to cause precipitation. The precipitate was collectedby filtration: This operation was conducted twice for purification.

As a result, a resin having a weight-average molecular weight of about2.0×10⁴ was obtained in yield of 75%. This resin is called as resin X4.Resin X4 had the following structural unit.

Examples 1 to 14 and Comparative Examples 1 to 3 Production ofPhotoresist Compositions

The following components as listed in Table 3 were mixed and dissolvedin the solvent as mentioned below, and then filtrated through afluororesin filter having pore diameter of 0.2 μm, to preparephotoresist compositions.

TABLE 3 Acid Compound Resin generator of formula Quencher PB (kind/(kind/ (I) (kind/ (kind/ (° C.)/ Comp. amount amount amount amount PEBNo. (part)) (part)) (part)) (part)) (° C.) Comp. 1 A1/10 B1-5/0.10I-19/0.35 D1/0.34 90/90 X1/0.7 B1-22/0.40 Comp. 2 A1/10 B1-21/0.95I-19/0.35 D1/0.34 90/90 X1/0.7 B1-22/0.40 Comp. 3 A2/10 B1-21/0.35I-19/0.35 D1/0.34 125/125 X1/0.7 B1-22/0.40 Comp. 4 A2/10 None I-19/0.35C1/0.1 125/125 X1/0.7 Comp. 5 A1/10 B1-22/0.4 I-19/0.45 D1/0.34 90/90X1/0.7 Comp. 6 A1/10 B1-21/0.95 I-20/0.25 D1/0.34 90/90 X1/0.7 Comp. 7A1/10 None I-20/0.40 D1/0.34 90/90 X1/0.7 I-19/0.95 Comp. 8 A1/10B1-22/0.40 I-49/0.45 D1/0.34 90/90 X1/0.7 Comp. 9 A1/10 B1-21/0.95I-50/0.25 D1/0.34 90/90 X1/0.7 Comp. 10 A1/10 None I-50/0.40 D1/0.3490/90 X1/0.7 I-49/0.95 Comp. 11 A1/10 B1-22/0.40 I-55/0.90 D1/0.34 90/90X1/0.7 Comp. 12 A1/10 None I-50/0.40 D1/0.34 90/90 X2/0.7 I-49/0.95Comp. 13 A1/10 None I-50/0.40 D1/0.34 90/90 X3/0.7 I-49/0.95 Comp. 14A1/10 None I-50/0.40 D1/0.34 90/90 X4/0.7 I-49/0.95 Compar. A2/10B1-3/0.85 None C1/0.10 125/125 Comp. 1 Compar. A2/10 IX-1/0.85 NoneC2/0.10 125/125 Comp. 2 Compar. A2/10 None I-19/0.85 C1/0.1 125/125Comp. 3

In Table 3, each of symbols represents the following component:

<Resin>

A1: Resin A1, A2: Resin A2, X1: Resin X1, X2: Resin X2,

X3: Resin X3, X4: Resin X4

<Acid Generator>

B1-3: Salt represented by formula (B1-3)

B1-5: Salt represented by formula (B1-5)

B1-21: Salt represented by formula (B1-21)

B1-22: Salt represented by formula (B1-22)

IX-1: Salt represented by formula (IX-1)

<Salt Represented by Formula (I)>

I-19: The compound represented by formula (I-19)

I-20: The compound represented by formula (I-20)

I-49: The compound represented by formula (I-49)

I-50: The compound represented by formula (I-50)

I-55: The compound represented by formula (I-55)

<Quencher>

C1: 2,6-diisopropylaniline

C2: The compound of the following formula:

D1: The compound of the following formula:

<Solvent>

Mixture of the following solvents propyleneglycolmonomethylether acetate265 parts propyleneglycolmonomethylether 20 parts 2-heptanone 20 partsγ-butyrolactone 3.5 parts

<Evaluation>

Silicon wafers (12 inches) were each coated with “ARC-29”, which is anorganic anti-reflective coating composition available from NissanChemical Industries, Ltd., and then baked at 205° C. for 60 seconds, toform a 78 nm-thick organic anti-reflective coating.

Each of the photoresist compositions prepared as above was spin-coatedover the anti-reflective coating so that the thickness of the resultingfilm became 85 nm after drying. The silicon wafers thus coated with therespective photoresist compositions were each prebaked on a directhotplate at a temperature shown in the column “PB” in Table 3 for 60seconds. Using an ArF excimer stepper for immersion exposure (“XT:1900Gi” manufactured by ASML, NA=1.35, 3/4 Annular, X—Y polarization),each wafer thus formed with the respective resist film was subjected toexposure with the exposure quantity being varied stepwise. For theexposure, a photomask for forming a contact hole pattern, which has 90nm of its pitch and 55 nm of the hole diameter, was used. Ultrapurewater was used as an immersion medium.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at a temperature shown in the column “PEB” in Table 3 for 60seconds and then to development in the manner of dynamic dispense methodat 23° C. for 20 seconds with butyl acetate (manufactured by TokyoChemical Industries, Co., Ltd) to make a photoresist pattern.

Effective sensitivity (ES): It was expressed as the exposure quantitythat the hole diameter became 50 nm after development.

CD uniformity (CDU): The photoresist patterns obtained with the exposureat ES using the above-mentioned photomask were observed with a scanningelectron microscope.

The hole diameter of the contact hole pattern was determined bymeasuring a distance between across two points on its circle, whichdistance corresponds to its diameter, at 24 sites of the circle. Theaverage of the measured values was regarded as the average holediameter.

The standard deviation (CDU) was calculated under the condition that theaverage diameter of four hundred holes about the patterns obtained withthe exposure at ES using a photomask with a hole diameter of 70 nm wasregarded to as population. Each of the standard deviation is shown inparentheses in a column of “CDU”.

The results of evaluation were marked as follow, and listed in Table 4.

TABLE 4 Ex. No. Composition CDU(nm) Ex. 1 Comp. 1 1.82 Ex. 2 Comp. 21.80 Ex. 3 Comp. 3 1.92 Ex. 4 Comp. 4 2.06 Ex. 5 Comp. 5 1.79 Ex. 6Comp. 6 1.81 Ex. 7 Comp. 7 1.76 Ex. 8 Comp. 8 1.74 Ex. 9 Comp. 9 1.75Ex. 10 Comp. 10 1.72 Ex. 11 Comp. 11 1.88 Ex. 12 Comp. 12 1.70 Ex. 13Comp. 13 1.68 Ex. 14 Comp. 14 1.68 Comp. Ex. 1 Compar. Comp. 1 2.22Comp. Ex. 2 Compar. Comp. 2 2.68 Comp. Ex. 3 Compar. Comp. 3 2.08

The photoresist composition of the disclosure can show an excellent CDuniformity when a photoresist pattern is made from it.

What is claimed is:
 1. A photoresist composition comprising a resinhaving an acid-labile group and no fluorine atom, a resin having afluorine atom, and a salt represented by formula (I):

in which X represents a sulfur atom or an iodine atom; m represents 0 or1; R¹ represents a C1-C12 fluoroalkyl group; R² and R³ eachindependently represent a C1-C12 hydrocarbon group in which a hydrogenatom can be replaced by a substituent and in which a methylene group canbe replaced by an oxygen atom, a sulfur atom or a carbonyl group, or R²and R³ are optionally bond to each other and form a ring together withX⁺ when X is a sulfur atom; and Z⁻ represents an organic anion.
 2. Thephotoresist composition according to claim 1 wherein R² represents aC6-C12 aromatic hydrocarbon group in which a hydrogen atom can bereplaced by a substituent.
 3. The photoresist composition according toclaim 1 wherein Z⁻ represents an organic anion represented by formula(I-A):

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group, L^(b1) represents a C1-C24 divalentsaturated hydrocarbon group in which a methylene group can be replacedby —O— or —CO— and in which a hydrogen atom can be replaced by afluorine atom or a hydroxy group, and Y represents a methyl group whichmay have a substituent or a C3-C18 alicyclic hydrocarbon group which canhave a substituent and in which a methylene group can be replaced by—O—, —CO— or —SO₂—.
 4. The photoresist composition according to claim 1wherein the resin having a fluorine atom comprises a structural unitrepresented by formula (a4-0), formula (a4-2), formula (a4-3), orformula (a4-4):

wherein R⁵ represents a hydrogen atom or a methyl group; L⁴ represents asingle bond or a C1-C4 aliphatic saturated hydrocarbon group; L³represents a C1-C8 perfluoroalkanediyl group; and R⁶ represents ahydrogen atom or a fluorine atom;

wherein R^(f1) represents a hydrogen atom or a methyl group; A^(f1)represents a C1-C6 alkanediyl group; and R^(f2) represents a C1-C10hydrocarbon group having a fluorine atom;

wherein R^(f11) represents a hydrogen atom or a methyl group; A^(f11)represents a C1-C6 alkanediyl group; A^(f13) represents a C1-C18aliphatic hydrocarbon group which may have a fluorine atom; X^(f12)represents a carbonyloxy group or an oxycarbonyl group; A^(f14)represents a C1-C17 aliphatic hydrocarbon group which may have afluorine atom, provided that one or both of A^(f13) and A^(f14)represents a fluorine-containing aliphatic hydrocarbon group;

wherein R^(f21) represents a hydrogen atom or a methyl group; A^(f21)represents —(CH₂)_(j1)—, —(CH₂)_(j2)—O—(CH₂)_(j3)— or—(CH₂)_(j4)—CO—O—(CH₂)_(j5)— where j1, j2, j3, j4 or j5 eachindependently represent an integer of 1 to 6; and R^(f22) represents aC1-C10 hydrocarbon group having a fluorine atom.
 5. The photoresistcomposition according to claim 1 which further comprises a salt whichgenerates an acid having acidity weaker than an acid generated from thesalt represented by formula (I).
 6. The photoresist compositionaccording to claim 5 wherein the salt which generates an acid havingacidity weaker than an acid generated from the salt represented byformula (I) is a compound represented by formula (D):

wherein R^(D1) and R^(D2) each independently represent a C1-C12monovalent hydrocarbon group, a C1-C6 alkoxy group, a C2-C7 acyl group,a C2-C7 acyloxy group, a C2-C7 alkoxycarbonyl group, a nitro group or ahalogen atom; and the symbols m′ and n′ each independently represent aninteger of 0 to
 4. 7. A process for producing a photoresist patterncomprising the following steps (1) to (5): (1) a step of applying thephotoresist composition according claim 1 on a substrate, (2) a step offorming a composition film by conducting drying, (3) a step of exposingthe composition film to radiation, (4) a step of baking the exposedcomposition film, and (5) a step of developing the baked compositionfilm.